<?xml version="1.0" encoding="UTF-8"?>

<!--XBRL Document Created with Wdesk from Workiva-->
<!--Copyright 2023 Workiva-->
<!--r:e4695471-33d7-4d4a-ad6a-7d74b49af35c,g:b181c997-0bf8-45dc-aed8-c4083beed63d-->
<link:linkbase xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd">
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/all" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-default"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member"/>
  <link:roleRef roleURI="http://www.suncountry.com/role/CONDENSEDCONSOLIDATEDBALANCESHEETS" xlink:type="simple" xlink:href="sncy-20230331.xsd#CONDENSEDCONSOLIDATEDBALANCESHEETS"/>
  <link:definitionLink xlink:role="http://www.suncountry.com/role/CONDENSEDCONSOLIDATEDBALANCESHEETS" xlink:type="extended" id="i80f6b1f1253843d18de22a2ba3706bc1_CONDENSEDCONSOLIDATEDBALANCESHEETS">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_f2bb6349-3d65-4fb7-9f88-609ec5139602" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsAbstract_f1240254-0b01-4d5f-9cce-1d8b45b4f167" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AssetsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_f2bb6349-3d65-4fb7-9f88-609ec5139602" xlink:to="loc_us-gaap_AssetsAbstract_f1240254-0b01-4d5f-9cce-1d8b45b4f167" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsCurrentAbstract_78fbc808-f3c2-4ff3-a11b-8ac0e7f4d61c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AssetsCurrentAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_f1240254-0b01-4d5f-9cce-1d8b45b4f167" xlink:to="loc_us-gaap_AssetsCurrentAbstract_78fbc808-f3c2-4ff3-a11b-8ac0e7f4d61c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_a5fcca7e-35e7-4d1d-aace-7819856bf03b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_78fbc808-f3c2-4ff3-a11b-8ac0e7f4d61c" xlink:to="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_a5fcca7e-35e7-4d1d-aace-7819856bf03b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashCurrent_08a0fbab-8bcb-4d44-9830-6ae9cb48da49" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RestrictedCashCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_78fbc808-f3c2-4ff3-a11b-8ac0e7f4d61c" xlink:to="loc_us-gaap_RestrictedCashCurrent_08a0fbab-8bcb-4d44-9830-6ae9cb48da49" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermInvestments_7806d153-f5d2-42ba-867d-43045d6ef5d7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShortTermInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_78fbc808-f3c2-4ff3-a11b-8ac0e7f4d61c" xlink:to="loc_us-gaap_ShortTermInvestments_7806d153-f5d2-42ba-867d-43045d6ef5d7" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsReceivableNetCurrent_ef1a4b36-50cd-4728-972e-ad2478e316c7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccountsReceivableNetCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_78fbc808-f3c2-4ff3-a11b-8ac0e7f4d61c" xlink:to="loc_us-gaap_AccountsReceivableNetCurrent_ef1a4b36-50cd-4728-972e-ad2478e316c7" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DepositsAssetsCurrent_8dffbeae-6cde-42da-bc38-c9006480b6f4" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DepositsAssetsCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_78fbc808-f3c2-4ff3-a11b-8ac0e7f4d61c" xlink:to="loc_us-gaap_DepositsAssetsCurrent_8dffbeae-6cde-42da-bc38-c9006480b6f4" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InventoryNet_9fff2444-89b7-4d7c-8a33-94e199bb01cc" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_InventoryNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_78fbc808-f3c2-4ff3-a11b-8ac0e7f4d61c" xlink:to="loc_us-gaap_InventoryNet_9fff2444-89b7-4d7c-8a33-94e199bb01cc" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PrepaidExpenseCurrent_37e83b99-429c-43c2-8e9c-18a649f26253" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PrepaidExpenseCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_78fbc808-f3c2-4ff3-a11b-8ac0e7f4d61c" xlink:to="loc_us-gaap_PrepaidExpenseCurrent_37e83b99-429c-43c2-8e9c-18a649f26253" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssetsCurrent_efc3ceca-5444-466b-a037-9140d0a10e5f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherAssetsCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_78fbc808-f3c2-4ff3-a11b-8ac0e7f4d61c" xlink:to="loc_us-gaap_OtherAssetsCurrent_efc3ceca-5444-466b-a037-9140d0a10e5f" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsCurrent_0c8ef767-c812-4b0b-ae78-85aef1a04e8a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AssetsCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_78fbc808-f3c2-4ff3-a11b-8ac0e7f4d61c" xlink:to="loc_us-gaap_AssetsCurrent_0c8ef767-c812-4b0b-ae78-85aef1a04e8a" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentNetAbstract_fa41a113-2c52-47af-a5f7-0143e4b0aabe" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PropertyPlantAndEquipmentNetAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_f1240254-0b01-4d5f-9cce-1d8b45b4f167" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentNetAbstract_fa41a113-2c52-47af-a5f7-0143e4b0aabe" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentGross_91ff0672-0f30-4a26-86b0-dc900659c559" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PropertyPlantAndEquipmentGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentNetAbstract_fa41a113-2c52-47af-a5f7-0143e4b0aabe" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentGross_91ff0672-0f30-4a26-86b0-dc900659c559" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeaseRightOfUseAsset_b8b424bf-d084-449b-b13b-db965129528b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinanceLeaseRightOfUseAsset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentNetAbstract_fa41a113-2c52-47af-a5f7-0143e4b0aabe" xlink:to="loc_us-gaap_FinanceLeaseRightOfUseAsset_b8b424bf-d084-449b-b13b-db965129528b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetBeforeAccumulatedDepreciationAndAmortization_8a1e432f-3033-4e98-b30f-fa71f76dc224" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetBeforeAccumulatedDepreciationAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentNetAbstract_fa41a113-2c52-47af-a5f7-0143e4b0aabe" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetBeforeAccumulatedDepreciationAndAmortization_8a1e432f-3033-4e98-b30f-fa71f76dc224" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAccumulatedDepreciationAndAmortization_a9348d65-34b1-495c-b857-02ddb58c63c5" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAccumulatedDepreciationAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentNetAbstract_fa41a113-2c52-47af-a5f7-0143e4b0aabe" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAccumulatedDepreciationAndAmortization_a9348d65-34b1-495c-b857-02ddb58c63c5" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAfterAccumulatedDepreciationAndAmortization_9236ec83-7d18-4f97-bb94-0df04d7cba77" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAfterAccumulatedDepreciationAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentNetAbstract_fa41a113-2c52-47af-a5f7-0143e4b0aabe" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAfterAccumulatedDepreciationAndAmortization_9236ec83-7d18-4f97-bb94-0df04d7cba77" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssetsAbstract_218b633f-63a4-4b25-8e28-7231ea04c6bf" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherAssetsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_f1240254-0b01-4d5f-9cce-1d8b45b4f167" xlink:to="loc_us-gaap_OtherAssetsAbstract_218b633f-63a4-4b25-8e28-7231ea04c6bf" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_da487e75-65b4-403b-8081-25a6c8a5bd36" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_Goodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherAssetsAbstract_218b633f-63a4-4b25-8e28-7231ea04c6bf" xlink:to="loc_us-gaap_Goodwill_da487e75-65b4-403b-8081-25a6c8a5bd36" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IntangibleAssetsNetExcludingGoodwill_ece72e2c-0678-4701-a9cb-7e325b99dd99" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IntangibleAssetsNetExcludingGoodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherAssetsAbstract_218b633f-63a4-4b25-8e28-7231ea04c6bf" xlink:to="loc_us-gaap_IntangibleAssetsNetExcludingGoodwill_ece72e2c-0678-4701-a9cb-7e325b99dd99" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseRightOfUseAsset_b27430a9-bbf9-47fe-8369-b10dc3b4e3d3" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OperatingLeaseRightOfUseAsset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherAssetsAbstract_218b633f-63a4-4b25-8e28-7231ea04c6bf" xlink:to="loc_us-gaap_OperatingLeaseRightOfUseAsset_b27430a9-bbf9-47fe-8369-b10dc3b4e3d3" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_AircraftLeaseDeposits_9942268f-19d0-42d4-bb86-2b0519c1baa7" xlink:href="sncy-20230331.xsd#sncy_AircraftLeaseDeposits"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherAssetsAbstract_218b633f-63a4-4b25-8e28-7231ea04c6bf" xlink:to="loc_sncy_AircraftLeaseDeposits_9942268f-19d0-42d4-bb86-2b0519c1baa7" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DepositsAssetsNoncurrent_4bbb700b-d660-4fc0-8d6d-956b4aae9f06" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DepositsAssetsNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherAssetsAbstract_218b633f-63a4-4b25-8e28-7231ea04c6bf" xlink:to="loc_us-gaap_DepositsAssetsNoncurrent_4bbb700b-d660-4fc0-8d6d-956b4aae9f06" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredIncomeTaxAssetsNet_7efcf29e-91ba-45ae-a2d6-e6b9f4e157b5" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DeferredIncomeTaxAssetsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherAssetsAbstract_218b633f-63a4-4b25-8e28-7231ea04c6bf" xlink:to="loc_us-gaap_DeferredIncomeTaxAssetsNet_7efcf29e-91ba-45ae-a2d6-e6b9f4e157b5" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssetsMiscellaneousNoncurrent_e5ffa9b1-8361-405f-824e-7547b205d70a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherAssetsMiscellaneousNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherAssetsAbstract_218b633f-63a4-4b25-8e28-7231ea04c6bf" xlink:to="loc_us-gaap_OtherAssetsMiscellaneousNoncurrent_e5ffa9b1-8361-405f-824e-7547b205d70a" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssetsNoncurrent_6b993109-c2cb-4512-b251-a0120b6e651c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherAssetsNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherAssetsAbstract_218b633f-63a4-4b25-8e28-7231ea04c6bf" xlink:to="loc_us-gaap_OtherAssetsNoncurrent_6b993109-c2cb-4512-b251-a0120b6e651c" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Assets_722d2352-0c70-48ae-88ba-eccc9e25ace9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_Assets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_f1240254-0b01-4d5f-9cce-1d8b45b4f167" xlink:to="loc_us-gaap_Assets_722d2352-0c70-48ae-88ba-eccc9e25ace9" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_1edb7d42-2c53-49ec-a177-c7824de26551" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LiabilitiesAndStockholdersEquityAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_f2bb6349-3d65-4fb7-9f88-609ec5139602" xlink:to="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_1edb7d42-2c53-49ec-a177-c7824de26551" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesCurrentAbstract_aa31cf82-8f46-4e2b-95f7-8a5ffd3a34ea" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LiabilitiesCurrentAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_1edb7d42-2c53-49ec-a177-c7824de26551" xlink:to="loc_us-gaap_LiabilitiesCurrentAbstract_aa31cf82-8f46-4e2b-95f7-8a5ffd3a34ea" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsPayableCurrent_737e0032-63ce-4723-8636-344ebee0873e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccountsPayableCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_aa31cf82-8f46-4e2b-95f7-8a5ffd3a34ea" xlink:to="loc_us-gaap_AccountsPayableCurrent_737e0032-63ce-4723-8636-344ebee0873e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeRelatedLiabilitiesCurrent_98d016b4-001d-4faa-a73a-1e2cc4baadd1" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EmployeeRelatedLiabilitiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_aa31cf82-8f46-4e2b-95f7-8a5ffd3a34ea" xlink:to="loc_us-gaap_EmployeeRelatedLiabilitiesCurrent_98d016b4-001d-4faa-a73a-1e2cc4baadd1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccrualForTaxesOtherThanIncomeTaxesCurrent_e996a407-b6fb-4ebe-b61b-48720d29033d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccrualForTaxesOtherThanIncomeTaxesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_aa31cf82-8f46-4e2b-95f7-8a5ffd3a34ea" xlink:to="loc_us-gaap_AccrualForTaxesOtherThanIncomeTaxesCurrent_e996a407-b6fb-4ebe-b61b-48720d29033d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_AirTrafficLiabilitiesCurrent_0c965771-4130-4cb5-99ea-a4c248816ff7" xlink:href="sncy-20230331.xsd#sncy_AirTrafficLiabilitiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_aa31cf82-8f46-4e2b-95f7-8a5ffd3a34ea" xlink:to="loc_sncy_AirTrafficLiabilitiesCurrent_0c965771-4130-4cb5-99ea-a4c248816ff7" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeaseLiabilityCurrent_921f885e-aae7-48a2-8297-4733535a9770" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinanceLeaseLiabilityCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_aa31cf82-8f46-4e2b-95f7-8a5ffd3a34ea" xlink:to="loc_us-gaap_FinanceLeaseLiabilityCurrent_921f885e-aae7-48a2-8297-4733535a9770" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_LoyaltyProgramLiabilitiesCurrent_8b18aa50-2052-4e17-b05e-645ee8d344df" xlink:href="sncy-20230331.xsd#sncy_LoyaltyProgramLiabilitiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_aa31cf82-8f46-4e2b-95f7-8a5ffd3a34ea" xlink:to="loc_sncy_LoyaltyProgramLiabilitiesCurrent_8b18aa50-2052-4e17-b05e-645ee8d344df" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiabilityCurrent_1054205b-51f5-41e0-9254-7b18e371df8e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OperatingLeaseLiabilityCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_aa31cf82-8f46-4e2b-95f7-8a5ffd3a34ea" xlink:to="loc_us-gaap_OperatingLeaseLiabilityCurrent_1054205b-51f5-41e0-9254-7b18e371df8e" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtCurrent_144d1a1d-fad0-46f3-af0b-e6e151ada4ce" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongTermDebtCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_aa31cf82-8f46-4e2b-95f7-8a5ffd3a34ea" xlink:to="loc_us-gaap_LongTermDebtCurrent_144d1a1d-fad0-46f3-af0b-e6e151ada4ce" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_IncomeTaxReceivableAgreementLiabilityCurrent_06aa5d69-4d0f-4b46-81d9-951fba393e04" xlink:href="sncy-20230331.xsd#sncy_IncomeTaxReceivableAgreementLiabilityCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_aa31cf82-8f46-4e2b-95f7-8a5ffd3a34ea" xlink:to="loc_sncy_IncomeTaxReceivableAgreementLiabilityCurrent_06aa5d69-4d0f-4b46-81d9-951fba393e04" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherLiabilitiesCurrent_5116279d-b948-448c-b46b-4674fe24b365" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherLiabilitiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_aa31cf82-8f46-4e2b-95f7-8a5ffd3a34ea" xlink:to="loc_us-gaap_OtherLiabilitiesCurrent_5116279d-b948-448c-b46b-4674fe24b365" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesCurrent_e22562b7-aff7-4a1d-aa36-249f864c14ff" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LiabilitiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_aa31cf82-8f46-4e2b-95f7-8a5ffd3a34ea" xlink:to="loc_us-gaap_LiabilitiesCurrent_e22562b7-aff7-4a1d-aa36-249f864c14ff" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesNoncurrentAbstract_9221091a-a8a0-440e-b3cb-fc01db545e40" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LiabilitiesNoncurrentAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_1edb7d42-2c53-49ec-a177-c7824de26551" xlink:to="loc_us-gaap_LiabilitiesNoncurrentAbstract_9221091a-a8a0-440e-b3cb-fc01db545e40" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeaseLiabilityNoncurrent_ca8722e0-15bc-48da-9204-07bf23e0c892" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinanceLeaseLiabilityNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesNoncurrentAbstract_9221091a-a8a0-440e-b3cb-fc01db545e40" xlink:to="loc_us-gaap_FinanceLeaseLiabilityNoncurrent_ca8722e0-15bc-48da-9204-07bf23e0c892" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_LoyaltyProgramLiabilitiesNoncurrent_d5a2f172-139f-4dfa-b8e4-6e7d7f02c315" xlink:href="sncy-20230331.xsd#sncy_LoyaltyProgramLiabilitiesNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesNoncurrentAbstract_9221091a-a8a0-440e-b3cb-fc01db545e40" xlink:to="loc_sncy_LoyaltyProgramLiabilitiesNoncurrent_d5a2f172-139f-4dfa-b8e4-6e7d7f02c315" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiabilityNoncurrent_518cca61-84db-4b3b-bd96-c6518fba06f7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OperatingLeaseLiabilityNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesNoncurrentAbstract_9221091a-a8a0-440e-b3cb-fc01db545e40" xlink:to="loc_us-gaap_OperatingLeaseLiabilityNoncurrent_518cca61-84db-4b3b-bd96-c6518fba06f7" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtNoncurrent_663e49de-3ffa-4ed4-8733-96160295fc07" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongTermDebtNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesNoncurrentAbstract_9221091a-a8a0-440e-b3cb-fc01db545e40" xlink:to="loc_us-gaap_LongTermDebtNoncurrent_663e49de-3ffa-4ed4-8733-96160295fc07" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_IncomeTaxesReceivableAgreementNoncurrent_b37a9a2e-6953-4d04-806b-24e0a5f3bdb2" xlink:href="sncy-20230331.xsd#sncy_IncomeTaxesReceivableAgreementNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesNoncurrentAbstract_9221091a-a8a0-440e-b3cb-fc01db545e40" xlink:to="loc_sncy_IncomeTaxesReceivableAgreementNoncurrent_b37a9a2e-6953-4d04-806b-24e0a5f3bdb2" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherLiabilitiesNoncurrent_ef39b075-db94-47f2-815e-3fbb1a848356" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherLiabilitiesNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesNoncurrentAbstract_9221091a-a8a0-440e-b3cb-fc01db545e40" xlink:to="loc_us-gaap_OtherLiabilitiesNoncurrent_ef39b075-db94-47f2-815e-3fbb1a848356" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesNoncurrent_4f442e08-d1e0-4b4a-ab2f-396d8f224174" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LiabilitiesNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesNoncurrentAbstract_9221091a-a8a0-440e-b3cb-fc01db545e40" xlink:to="loc_us-gaap_LiabilitiesNoncurrent_4f442e08-d1e0-4b4a-ab2f-396d8f224174" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Liabilities_5a9637b8-4d1b-4d89-a7dc-82c9c2cc024f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_Liabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_1edb7d42-2c53-49ec-a177-c7824de26551" xlink:to="loc_us-gaap_Liabilities_5a9637b8-4d1b-4d89-a7dc-82c9c2cc024f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommitmentsAndContingencies_e682503f-b710-4e9a-9d1e-f15a0f5c1f39" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommitmentsAndContingencies"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_1edb7d42-2c53-49ec-a177-c7824de26551" xlink:to="loc_us-gaap_CommitmentsAndContingencies_e682503f-b710-4e9a-9d1e-f15a0f5c1f39" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_3f3f076a-c009-4ba6-a04c-5ac9184cccd9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_1edb7d42-2c53-49ec-a177-c7824de26551" xlink:to="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_3f3f076a-c009-4ba6-a04c-5ac9184cccd9" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockNumberOfSharesParValueAndOtherDisclosuresAbstract_7346a307-3da9-4131-a308-7740d4f4abf0" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonStockNumberOfSharesParValueAndOtherDisclosuresAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_3f3f076a-c009-4ba6-a04c-5ac9184cccd9" xlink:to="loc_us-gaap_CommonStockNumberOfSharesParValueAndOtherDisclosuresAbstract_7346a307-3da9-4131-a308-7740d4f4abf0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockValue_fd51b9f5-f0ff-424c-b931-9ebb2b627f77" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonStockValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CommonStockNumberOfSharesParValueAndOtherDisclosuresAbstract_7346a307-3da9-4131-a308-7740d4f4abf0" xlink:to="loc_us-gaap_CommonStockValue_fd51b9f5-f0ff-424c-b931-9ebb2b627f77" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockNumberOfSharesParValueAndOtherDisclosuresAbstract_bdcbc268-d93b-4b62-8491-40d6534a98af" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PreferredStockNumberOfSharesParValueAndOtherDisclosuresAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_3f3f076a-c009-4ba6-a04c-5ac9184cccd9" xlink:to="loc_us-gaap_PreferredStockNumberOfSharesParValueAndOtherDisclosuresAbstract_bdcbc268-d93b-4b62-8491-40d6534a98af" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockValue_78e02b90-2f20-4e40-ae9d-0060121d1a63" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PreferredStockValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PreferredStockNumberOfSharesParValueAndOtherDisclosuresAbstract_bdcbc268-d93b-4b62-8491-40d6534a98af" xlink:to="loc_us-gaap_PreferredStockValue_78e02b90-2f20-4e40-ae9d-0060121d1a63" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockCommonValue_4be2a59f-89b1-482b-a88f-f23aad3a3c1f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_TreasuryStockCommonValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PreferredStockNumberOfSharesParValueAndOtherDisclosuresAbstract_bdcbc268-d93b-4b62-8491-40d6534a98af" xlink:to="loc_us-gaap_TreasuryStockCommonValue_4be2a59f-89b1-482b-a88f-f23aad3a3c1f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapital_18665f9f-f7b3-4899-b650-86605c6f96bf" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AdditionalPaidInCapital"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_3f3f076a-c009-4ba6-a04c-5ac9184cccd9" xlink:to="loc_us-gaap_AdditionalPaidInCapital_18665f9f-f7b3-4899-b650-86605c6f96bf" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsAccumulatedDeficit_c478b5e0-1375-4a95-aa31-caccaf6222d8" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RetainedEarningsAccumulatedDeficit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_3f3f076a-c009-4ba6-a04c-5ac9184cccd9" xlink:to="loc_us-gaap_RetainedEarningsAccumulatedDeficit_c478b5e0-1375-4a95-aa31-caccaf6222d8" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_eddb0ebd-2fef-4c5c-8760-e9e2f431dfcf" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_3f3f076a-c009-4ba6-a04c-5ac9184cccd9" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_eddb0ebd-2fef-4c5c-8760-e9e2f431dfcf" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_7bc29b66-e977-4f0a-bd0c-e8ce4fc00e43" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_3f3f076a-c009-4ba6-a04c-5ac9184cccd9" xlink:to="loc_us-gaap_StockholdersEquity_7bc29b66-e977-4f0a-bd0c-e8ce4fc00e43" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesAndStockholdersEquity_01a4d5c8-bd1f-4ee0-8e88-429d2cef33b4" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LiabilitiesAndStockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_1edb7d42-2c53-49ec-a177-c7824de26551" xlink:to="loc_us-gaap_LiabilitiesAndStockholdersEquity_01a4d5c8-bd1f-4ee0-8e88-429d2cef33b4" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_84a75e4e-9fc7-4483-84b4-3f5eb75b59d0" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_f2bb6349-3d65-4fb7-9f88-609ec5139602" xlink:to="loc_us-gaap_StatementTable_84a75e4e-9fc7-4483-84b4-3f5eb75b59d0" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_194a2459-a95c-4228-b791-70259a4e60f3" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PropertyPlantAndEquipmentByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_84a75e4e-9fc7-4483-84b4-3f5eb75b59d0" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_194a2459-a95c-4228-b791-70259a4e60f3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_194a2459-a95c-4228-b791-70259a4e60f3_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_194a2459-a95c-4228-b791-70259a4e60f3" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_194a2459-a95c-4228-b791-70259a4e60f3_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_b2949ab0-13d3-49ad-8ac5-363d90129bd8" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_194a2459-a95c-4228-b791-70259a4e60f3" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_b2949ab0-13d3-49ad-8ac5-363d90129bd8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AirTransportationEquipmentMember_49669ec3-83e2-4b26-88d1-b7672bc18629" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AirTransportationEquipmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_b2949ab0-13d3-49ad-8ac5-363d90129bd8" xlink:to="loc_us-gaap_AirTransportationEquipmentMember_49669ec3-83e2-4b26-88d1-b7672bc18629" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_AircraftAndFlightEquipmentHeldForOperatingLeaseMember_34ab8d42-575a-4705-9809-09f5dfb24bad" xlink:href="sncy-20230331.xsd#sncy_AircraftAndFlightEquipmentHeldForOperatingLeaseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_b2949ab0-13d3-49ad-8ac5-363d90129bd8" xlink:to="loc_sncy_AircraftAndFlightEquipmentHeldForOperatingLeaseMember_34ab8d42-575a-4705-9809-09f5dfb24bad" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LeaseholdImprovementsMember_8e86f85f-910f-4133-9db0-9b336b742c58" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LeaseholdImprovementsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_b2949ab0-13d3-49ad-8ac5-363d90129bd8" xlink:to="loc_us-gaap_LeaseholdImprovementsMember_8e86f85f-910f-4133-9db0-9b336b742c58" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ComputerEquipmentMember_ea2e9153-e288-4a02-a78e-3874bd405b26" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ComputerEquipmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_b2949ab0-13d3-49ad-8ac5-363d90129bd8" xlink:to="loc_us-gaap_ComputerEquipmentMember_ea2e9153-e288-4a02-a78e-3874bd405b26" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_RotablePartsMember_c4de805a-698e-4d61-b9b3-33c90f747ff2" xlink:href="sncy-20230331.xsd#sncy_RotablePartsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_b2949ab0-13d3-49ad-8ac5-363d90129bd8" xlink:to="loc_sncy_RotablePartsMember_c4de805a-698e-4d61-b9b3-33c90f747ff2" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.suncountry.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFOPERATIONS" xlink:type="simple" xlink:href="sncy-20230331.xsd#CONDENSEDCONSOLIDATEDSTATEMENTSOFOPERATIONS"/>
  <link:definitionLink xlink:role="http://www.suncountry.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFOPERATIONS" xlink:type="extended" id="i88e352c002744cbeb9867e73552c56c5_CONDENSEDCONSOLIDATEDSTATEMENTSOFOPERATIONS">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_05bb071c-3ae6-4a3e-b578-4dd4d1cf20b8" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenuesAbstract_8caf6e9a-1004-41d1-bc7f-0546ce050c73" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RevenuesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_05bb071c-3ae6-4a3e-b578-4dd4d1cf20b8" xlink:to="loc_us-gaap_RevenuesAbstract_8caf6e9a-1004-41d1-bc7f-0546ce050c73" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_43484b4f-8797-43e0-8f89-c52b96ba6fec" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenuesAbstract_8caf6e9a-1004-41d1-bc7f-0546ce050c73" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_43484b4f-8797-43e0-8f89-c52b96ba6fec" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingExpensesAbstract_57782aad-e33b-49d0-bb74-3dde094c6fbc" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OperatingExpensesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_05bb071c-3ae6-4a3e-b578-4dd4d1cf20b8" xlink:to="loc_us-gaap_OperatingExpensesAbstract_57782aad-e33b-49d0-bb74-3dde094c6fbc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FuelCosts_bf5ff427-f2dd-4946-a770-6583bf55de8f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FuelCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_57782aad-e33b-49d0-bb74-3dde094c6fbc" xlink:to="loc_us-gaap_FuelCosts_bf5ff427-f2dd-4946-a770-6583bf55de8f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LaborAndRelatedExpense_bcc3e870-9f0b-4465-8b10-91b69e596e22" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LaborAndRelatedExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_57782aad-e33b-49d0-bb74-3dde094c6fbc" xlink:to="loc_us-gaap_LaborAndRelatedExpense_bcc3e870-9f0b-4465-8b10-91b69e596e22" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AircraftRental_f2c94d4a-88d5-4f9f-911b-52905c33843a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AircraftRental"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_57782aad-e33b-49d0-bb74-3dde094c6fbc" xlink:to="loc_us-gaap_AircraftRental_f2c94d4a-88d5-4f9f-911b-52905c33843a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AircraftMaintenanceMaterialsAndRepairs_e53159cc-49b2-4b46-bbe0-f9fe255888b7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AircraftMaintenanceMaterialsAndRepairs"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_57782aad-e33b-49d0-bb74-3dde094c6fbc" xlink:to="loc_us-gaap_AircraftMaintenanceMaterialsAndRepairs_e53159cc-49b2-4b46-bbe0-f9fe255888b7" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SellingAndMarketingExpense_8a5b8c62-f7e6-4c0f-9186-2466a4eded8c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SellingAndMarketingExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_57782aad-e33b-49d0-bb74-3dde094c6fbc" xlink:to="loc_us-gaap_SellingAndMarketingExpense_8a5b8c62-f7e6-4c0f-9186-2466a4eded8c" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DepreciationDepletionAndAmortization_4d90ea7c-186d-44b7-b564-240707825c5e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DepreciationDepletionAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_57782aad-e33b-49d0-bb74-3dde094c6fbc" xlink:to="loc_us-gaap_DepreciationDepletionAndAmortization_4d90ea7c-186d-44b7-b564-240707825c5e" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_GroundHandlingExpense_7b62f6f4-2d05-4da9-b5a1-917ae8839741" xlink:href="sncy-20230331.xsd#sncy_GroundHandlingExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_57782aad-e33b-49d0-bb74-3dde094c6fbc" xlink:to="loc_sncy_GroundHandlingExpense_7b62f6f4-2d05-4da9-b5a1-917ae8839741" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LandingFeesAndOtherRentals_54a2564b-83b2-46a5-9b66-a9e2a22c0b92" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LandingFeesAndOtherRentals"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_57782aad-e33b-49d0-bb74-3dde094c6fbc" xlink:to="loc_us-gaap_LandingFeesAndOtherRentals_54a2564b-83b2-46a5-9b66-a9e2a22c0b92" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherOperatingIncomeExpenseNet_11585e0b-34fa-4976-b779-09186042cc40" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherOperatingIncomeExpenseNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_57782aad-e33b-49d0-bb74-3dde094c6fbc" xlink:to="loc_us-gaap_OtherOperatingIncomeExpenseNet_11585e0b-34fa-4976-b779-09186042cc40" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostsAndExpenses_1fc1a67a-1779-4c2c-9831-3fcef295d582" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CostsAndExpenses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_57782aad-e33b-49d0-bb74-3dde094c6fbc" xlink:to="loc_us-gaap_CostsAndExpenses_1fc1a67a-1779-4c2c-9831-3fcef295d582" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingIncomeLoss_bc2b116a-afda-44fb-b17a-30fe63a3d8a9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OperatingIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_05bb071c-3ae6-4a3e-b578-4dd4d1cf20b8" xlink:to="loc_us-gaap_OperatingIncomeLoss_bc2b116a-afda-44fb-b17a-30fe63a3d8a9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonoperatingIncomeExpenseAbstract_69fb8db2-821b-49d8-bb11-bab87384d6ed" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_NonoperatingIncomeExpenseAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_05bb071c-3ae6-4a3e-b578-4dd4d1cf20b8" xlink:to="loc_us-gaap_NonoperatingIncomeExpenseAbstract_69fb8db2-821b-49d8-bb11-bab87384d6ed" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentIncomeInterest_2646a733-1716-45f4-a425-386898d92a68" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_InvestmentIncomeInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NonoperatingIncomeExpenseAbstract_69fb8db2-821b-49d8-bb11-bab87384d6ed" xlink:to="loc_us-gaap_InvestmentIncomeInterest_2646a733-1716-45f4-a425-386898d92a68" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpense_2c96560c-1b33-4fb0-a4ba-8377be48d0f9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_InterestExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NonoperatingIncomeExpenseAbstract_69fb8db2-821b-49d8-bb11-bab87384d6ed" xlink:to="loc_us-gaap_InterestExpense_2c96560c-1b33-4fb0-a4ba-8377be48d0f9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherNonoperatingIncomeExpense_5f93fc02-7382-4b21-879f-737d946e8f9e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherNonoperatingIncomeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NonoperatingIncomeExpenseAbstract_69fb8db2-821b-49d8-bb11-bab87384d6ed" xlink:to="loc_us-gaap_OtherNonoperatingIncomeExpense_5f93fc02-7382-4b21-879f-737d946e8f9e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonoperatingIncomeExpense_8e7249dd-c3a8-4286-87a2-cff9ec3d9883" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_NonoperatingIncomeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NonoperatingIncomeExpenseAbstract_69fb8db2-821b-49d8-bb11-bab87384d6ed" xlink:to="loc_us-gaap_NonoperatingIncomeExpense_8e7249dd-c3a8-4286-87a2-cff9ec3d9883" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_52ed74e2-74b6-4bfc-a7ac-0d64fcbaa774" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_05bb071c-3ae6-4a3e-b578-4dd4d1cf20b8" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_52ed74e2-74b6-4bfc-a7ac-0d64fcbaa774" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefit_2593a647-74b0-4d89-8a72-bac742957c41" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncomeTaxExpenseBenefit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_05bb071c-3ae6-4a3e-b578-4dd4d1cf20b8" xlink:to="loc_us-gaap_IncomeTaxExpenseBenefit_2593a647-74b0-4d89-8a72-bac742957c41" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_768b6b71-cfa1-4fdf-b917-c3bd31ba047b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_05bb071c-3ae6-4a3e-b578-4dd4d1cf20b8" xlink:to="loc_us-gaap_NetIncomeLoss_768b6b71-cfa1-4fdf-b917-c3bd31ba047b" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareAbstract_dab4f0fa-bd3e-48c7-b551-919f56bb6159" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EarningsPerShareAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_05bb071c-3ae6-4a3e-b578-4dd4d1cf20b8" xlink:to="loc_us-gaap_EarningsPerShareAbstract_dab4f0fa-bd3e-48c7-b551-919f56bb6159" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareBasic_eb67d550-5195-44b0-bda8-01cca0c3c7d7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EarningsPerShareBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareAbstract_dab4f0fa-bd3e-48c7-b551-919f56bb6159" xlink:to="loc_us-gaap_EarningsPerShareBasic_eb67d550-5195-44b0-bda8-01cca0c3c7d7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareDiluted_c76c2885-c86e-4a55-b541-4020af0424db" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EarningsPerShareDiluted"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareAbstract_dab4f0fa-bd3e-48c7-b551-919f56bb6159" xlink:to="loc_us-gaap_EarningsPerShareDiluted_c76c2885-c86e-4a55-b541-4020af0424db" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_92bd2bdd-c9e3-43c9-bf4c-a5ddf58e031f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_05bb071c-3ae6-4a3e-b578-4dd4d1cf20b8" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_92bd2bdd-c9e3-43c9-bf4c-a5ddf58e031f" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_2809c5a0-b445-4f5c-a26a-2785a96103a7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_92bd2bdd-c9e3-43c9-bf4c-a5ddf58e031f" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_2809c5a0-b445-4f5c-a26a-2785a96103a7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_e12389c7-542c-404b-b35a-b242bf5b3d54" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_92bd2bdd-c9e3-43c9-bf4c-a5ddf58e031f" xlink:to="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_e12389c7-542c-404b-b35a-b242bf5b3d54" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_dd3d2418-b4a1-415c-8987-9f9d9b8a3689" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_05bb071c-3ae6-4a3e-b578-4dd4d1cf20b8" xlink:to="loc_us-gaap_StatementTable_dd3d2418-b4a1-415c-8987-9f9d9b8a3689" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_50ba48b9-92a8-4310-8cd1-2ea05c63c74b" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_dd3d2418-b4a1-415c-8987-9f9d9b8a3689" xlink:to="loc_srt_ProductOrServiceAxis_50ba48b9-92a8-4310-8cd1-2ea05c63c74b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_50ba48b9-92a8-4310-8cd1-2ea05c63c74b_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_50ba48b9-92a8-4310-8cd1-2ea05c63c74b" xlink:to="loc_srt_ProductsAndServicesDomain_50ba48b9-92a8-4310-8cd1-2ea05c63c74b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_3198790e-b799-4f4a-b48c-d4f2ab4835f4" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_50ba48b9-92a8-4310-8cd1-2ea05c63c74b" xlink:to="loc_srt_ProductsAndServicesDomain_3198790e-b799-4f4a-b48c-d4f2ab4835f4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PassengerMember_c4ba31cc-0054-4f49-aa2e-2ff2688ed844" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PassengerMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_3198790e-b799-4f4a-b48c-d4f2ab4835f4" xlink:to="loc_us-gaap_PassengerMember_c4ba31cc-0054-4f49-aa2e-2ff2688ed844" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CargoAndFreightMember_6e466134-374f-4035-9802-72e43cbb23e1" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CargoAndFreightMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_3198790e-b799-4f4a-b48c-d4f2ab4835f4" xlink:to="loc_us-gaap_CargoAndFreightMember_6e466134-374f-4035-9802-72e43cbb23e1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ServiceOtherMember_c3732687-31fa-4b35-8cde-76791cbef5c4" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ServiceOtherMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_3198790e-b799-4f4a-b48c-d4f2ab4835f4" xlink:to="loc_us-gaap_ServiceOtherMember_c3732687-31fa-4b35-8cde-76791cbef5c4" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.suncountry.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFCHANGESINSTOCKHOLDERSEQUITY" xlink:type="simple" xlink:href="sncy-20230331.xsd#CONDENSEDCONSOLIDATEDSTATEMENTSOFCHANGESINSTOCKHOLDERSEQUITY"/>
  <link:definitionLink xlink:role="http://www.suncountry.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFCHANGESINSTOCKHOLDERSEQUITY" xlink:type="extended" id="iceb3cd036477481e85b7d901814e5dca_CONDENSEDCONSOLIDATEDSTATEMENTSOFCHANGESINSTOCKHOLDERSEQUITY">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_a45afdb5-3b3c-4bc3-a2d2-c7e68c35d3a0" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_8f31ea9d-fd9d-488d-bfe5-1d5db8cf7c63" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncreaseDecreaseInStockholdersEquityRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_a45afdb5-3b3c-4bc3-a2d2-c7e68c35d3a0" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_8f31ea9d-fd9d-488d-bfe5-1d5db8cf7c63" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharesOutstanding_9245a68c-76c5-406b-8eea-eeae3e3136fa" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_8f31ea9d-fd9d-488d-bfe5-1d5db8cf7c63" xlink:to="loc_us-gaap_SharesOutstanding_9245a68c-76c5-406b-8eea-eeae3e3136fa" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_016e5557-d3d0-4b97-bb02-870d6812d164" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_8f31ea9d-fd9d-488d-bfe5-1d5db8cf7c63" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_016e5557-d3d0-4b97-bb02-870d6812d164" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_6a346c1d-826c-4d0f-ad2d-69cba2784bde" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_8f31ea9d-fd9d-488d-bfe5-1d5db8cf7c63" xlink:to="loc_us-gaap_StockholdersEquity_6a346c1d-826c-4d0f-ad2d-69cba2784bde" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockCommonShares_2431c090-93eb-41a5-9ffb-ab6ae38e9ee9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_TreasuryStockCommonShares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_8f31ea9d-fd9d-488d-bfe5-1d5db8cf7c63" xlink:to="loc_us-gaap_TreasuryStockCommonShares_2431c090-93eb-41a5-9ffb-ab6ae38e9ee9" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod_9a502992-bb1c-46ca-a325-964b7cd49e47" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_8f31ea9d-fd9d-488d-bfe5-1d5db8cf7c63" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod_9a502992-bb1c-46ca-a325-964b7cd49e47" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation_3020fb2e-e88e-4647-9a3c-a02b12f2d236" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_8f31ea9d-fd9d-488d-bfe5-1d5db8cf7c63" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation_3020fb2e-e88e-4647-9a3c-a02b12f2d236" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardNetOfForfeitures_c556389b-d6c0-44fe-95fd-d24eacda62a8" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardNetOfForfeitures"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_8f31ea9d-fd9d-488d-bfe5-1d5db8cf7c63" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardNetOfForfeitures_c556389b-d6c0-44fe-95fd-d24eacda62a8" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_SharesSurrenderedByStockholdersValueInExchangeOfPromissoryNotes_74893172-9427-40ed-96c8-a99fc9c7790f" xlink:href="sncy-20230331.xsd#sncy_SharesSurrenderedByStockholdersValueInExchangeOfPromissoryNotes"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_8f31ea9d-fd9d-488d-bfe5-1d5db8cf7c63" xlink:to="loc_sncy_SharesSurrenderedByStockholdersValueInExchangeOfPromissoryNotes_74893172-9427-40ed-96c8-a99fc9c7790f" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockSharesAcquired_a6aab3f8-718a-44d5-b93a-df6ad2fd422c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_TreasuryStockSharesAcquired"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_8f31ea9d-fd9d-488d-bfe5-1d5db8cf7c63" xlink:to="loc_us-gaap_TreasuryStockSharesAcquired_a6aab3f8-718a-44d5-b93a-df6ad2fd422c" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockValueAcquiredCostMethod_44ea3a92-078c-4a92-ac68-391509107155" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_TreasuryStockValueAcquiredCostMethod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_8f31ea9d-fd9d-488d-bfe5-1d5db8cf7c63" xlink:to="loc_us-gaap_TreasuryStockValueAcquiredCostMethod_44ea3a92-078c-4a92-ac68-391509107155" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_4389c35d-daee-4e0e-82ed-ef17ec7e8ac3" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_8f31ea9d-fd9d-488d-bfe5-1d5db8cf7c63" xlink:to="loc_us-gaap_NetIncomeLoss_4389c35d-daee-4e0e-82ed-ef17ec7e8ac3" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_WarrantsVested_6e371749-92b0-46d6-89e1-be6ccc10a56b" xlink:href="sncy-20230331.xsd#sncy_WarrantsVested"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_8f31ea9d-fd9d-488d-bfe5-1d5db8cf7c63" xlink:to="loc_sncy_WarrantsVested_6e371749-92b0-46d6-89e1-be6ccc10a56b" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalWarrantIssued_aff4d81e-ab85-46dc-8697-2c0943bc4b9d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalWarrantIssued"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_8f31ea9d-fd9d-488d-bfe5-1d5db8cf7c63" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalWarrantIssued_aff4d81e-ab85-46dc-8697-2c0943bc4b9d" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_092580d1-8961-45c8-8835-f4934b745734" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_8f31ea9d-fd9d-488d-bfe5-1d5db8cf7c63" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_092580d1-8961-45c8-8835-f4934b745734" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_23f9a679-84d9-4028-b44b-85366df0a084" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_8f31ea9d-fd9d-488d-bfe5-1d5db8cf7c63" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_23f9a679-84d9-4028-b44b-85366df0a084" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharesOutstanding_7da2be0e-b7b9-4aa2-b0e2-d8470d0354b2" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SharesOutstanding"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_5e6cba58-0533-4603-ac63-b4b0c0c526b6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_242a02bc-c0fa-4678-8c08-f061524c5ac3" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockholdersEquity"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockCommonShares_93643834-09e3-423e-bb2c-c18ac6728530" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_TreasuryStockCommonShares"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_596eb6d8-0094-47ab-847f-162413c1c1f4" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_a45afdb5-3b3c-4bc3-a2d2-c7e68c35d3a0" xlink:to="loc_us-gaap_StatementTable_596eb6d8-0094-47ab-847f-162413c1c1f4" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_301878e6-f04c-4518-a175-3dacd81284dd" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_596eb6d8-0094-47ab-847f-162413c1c1f4" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_301878e6-f04c-4518-a175-3dacd81284dd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_301878e6-f04c-4518-a175-3dacd81284dd_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_301878e6-f04c-4518-a175-3dacd81284dd" xlink:to="loc_us-gaap_EquityComponentDomain_301878e6-f04c-4518-a175-3dacd81284dd_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_2d6ad738-06c4-43ec-9a85-705865e8247b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_301878e6-f04c-4518-a175-3dacd81284dd" xlink:to="loc_us-gaap_EquityComponentDomain_2d6ad738-06c4-43ec-9a85-705865e8247b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WarrantMember_5bd374e9-cf23-401a-ad06-2fa74fa1caef" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_WarrantMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_2d6ad738-06c4-43ec-9a85-705865e8247b" xlink:to="loc_us-gaap_WarrantMember_5bd374e9-cf23-401a-ad06-2fa74fa1caef" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_f8985b62-7e92-4434-8974-cc934e6dc1c1" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_2d6ad738-06c4-43ec-9a85-705865e8247b" xlink:to="loc_us-gaap_CommonStockMember_f8985b62-7e92-4434-8974-cc934e6dc1c1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockCommonMember_d50db0a4-1ef3-4ce8-aef2-bbf89e36d026" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_TreasuryStockCommonMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_2d6ad738-06c4-43ec-9a85-705865e8247b" xlink:to="loc_us-gaap_TreasuryStockCommonMember_d50db0a4-1ef3-4ce8-aef2-bbf89e36d026" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalMember_914ae6ac-674e-423e-8504-23258bf47147" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AdditionalPaidInCapitalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_2d6ad738-06c4-43ec-9a85-705865e8247b" xlink:to="loc_us-gaap_AdditionalPaidInCapitalMember_914ae6ac-674e-423e-8504-23258bf47147" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsMember_c2bcb9ea-8c65-407e-b77e-e71d54db9440" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RetainedEarningsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_2d6ad738-06c4-43ec-9a85-705865e8247b" xlink:to="loc_us-gaap_RetainedEarningsMember_c2bcb9ea-8c65-407e-b77e-e71d54db9440" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_ddec8305-0f4b-4fee-9bb2-75aee4e2282e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_2d6ad738-06c4-43ec-9a85-705865e8247b" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_ddec8305-0f4b-4fee-9bb2-75aee4e2282e" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.suncountry.com/role/REVENUESignificantCategoriesofOperatingRevenuesDetails" xlink:type="simple" xlink:href="sncy-20230331.xsd#REVENUESignificantCategoriesofOperatingRevenuesDetails"/>
  <link:definitionLink xlink:role="http://www.suncountry.com/role/REVENUESignificantCategoriesofOperatingRevenuesDetails" xlink:type="extended" id="if3a7424d6fe942dfbf2cac1485b08061_REVENUESignificantCategoriesofOperatingRevenuesDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_db13c9a6-4486-4b4a-8912-371c7394794a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DisaggregationOfRevenueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_a3e4d7a7-9150-41c5-afce-1d5af28d0111" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_db13c9a6-4486-4b4a-8912-371c7394794a" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_a3e4d7a7-9150-41c5-afce-1d5af28d0111" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_a9d466eb-d1cb-4d2e-bf50-87ea4dbfd43a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DisaggregationOfRevenueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_db13c9a6-4486-4b4a-8912-371c7394794a" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_a9d466eb-d1cb-4d2e-bf50-87ea4dbfd43a" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_84e5a35a-e015-454d-9d76-1535689bd05e" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_a9d466eb-d1cb-4d2e-bf50-87ea4dbfd43a" xlink:to="loc_srt_ProductOrServiceAxis_84e5a35a-e015-454d-9d76-1535689bd05e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_84e5a35a-e015-454d-9d76-1535689bd05e_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_84e5a35a-e015-454d-9d76-1535689bd05e" xlink:to="loc_srt_ProductsAndServicesDomain_84e5a35a-e015-454d-9d76-1535689bd05e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_49d50754-381f-4bd3-b5e1-9372b17d330f" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_84e5a35a-e015-454d-9d76-1535689bd05e" xlink:to="loc_srt_ProductsAndServicesDomain_49d50754-381f-4bd3-b5e1-9372b17d330f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PassengerMember_2e8d65d1-d488-4878-8769-05cc7b3d910a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PassengerMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_49d50754-381f-4bd3-b5e1-9372b17d330f" xlink:to="loc_us-gaap_PassengerMember_2e8d65d1-d488-4878-8769-05cc7b3d910a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_ScheduledServiceMember_341873ef-fc28-47a1-b32c-7acf80221616" xlink:href="sncy-20230331.xsd#sncy_ScheduledServiceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PassengerMember_2e8d65d1-d488-4878-8769-05cc7b3d910a" xlink:to="loc_sncy_ScheduledServiceMember_341873ef-fc28-47a1-b32c-7acf80221616" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_CharterServiceMember_2499b4cf-6132-4a0f-9890-c4c9921382fb" xlink:href="sncy-20230331.xsd#sncy_CharterServiceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PassengerMember_2e8d65d1-d488-4878-8769-05cc7b3d910a" xlink:to="loc_sncy_CharterServiceMember_2499b4cf-6132-4a0f-9890-c4c9921382fb" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_AncillaryMember_f8bda5c7-ed3d-48af-8d3a-a3f42ee69e7f" xlink:href="sncy-20230331.xsd#sncy_AncillaryMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PassengerMember_2e8d65d1-d488-4878-8769-05cc7b3d910a" xlink:to="loc_sncy_AncillaryMember_f8bda5c7-ed3d-48af-8d3a-a3f42ee69e7f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CargoAndFreightMember_9c56f6a3-a3d6-4c7c-9cf2-bc67cd79c735" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CargoAndFreightMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_49d50754-381f-4bd3-b5e1-9372b17d330f" xlink:to="loc_us-gaap_CargoAndFreightMember_9c56f6a3-a3d6-4c7c-9cf2-bc67cd79c735" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ServiceOtherMember_90c0df7d-01af-4b71-9395-510cbf36557a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ServiceOtherMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_49d50754-381f-4bd3-b5e1-9372b17d330f" xlink:to="loc_us-gaap_ServiceOtherMember_90c0df7d-01af-4b71-9395-510cbf36557a" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.suncountry.com/role/REVENUEOperatingRevenuesbyGeographicRegionDetails" xlink:type="simple" xlink:href="sncy-20230331.xsd#REVENUEOperatingRevenuesbyGeographicRegionDetails"/>
  <link:definitionLink xlink:role="http://www.suncountry.com/role/REVENUEOperatingRevenuesbyGeographicRegionDetails" xlink:type="extended" id="id297902b6ef541c3b6e8181bb4fd7ceb_REVENUEOperatingRevenuesbyGeographicRegionDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_73765040-abf7-439e-8e04-8fab072e6c8a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DisaggregationOfRevenueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_f4c29059-ae81-4ad1-b271-23b4098a87b2" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_73765040-abf7-439e-8e04-8fab072e6c8a" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_f4c29059-ae81-4ad1-b271-23b4098a87b2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_891a4329-fc9b-4283-8297-55cb9b08b0c1" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DisaggregationOfRevenueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_73765040-abf7-439e-8e04-8fab072e6c8a" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_891a4329-fc9b-4283-8297-55cb9b08b0c1" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_f199e32b-0960-47e7-a810-b21e37cd3740" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_StatementGeographicalAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_891a4329-fc9b-4283-8297-55cb9b08b0c1" xlink:to="loc_srt_StatementGeographicalAxis_f199e32b-0960-47e7-a810-b21e37cd3740" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_f199e32b-0960-47e7-a810-b21e37cd3740_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_f199e32b-0960-47e7-a810-b21e37cd3740" xlink:to="loc_srt_SegmentGeographicalDomain_f199e32b-0960-47e7-a810-b21e37cd3740_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_db535229-b2fa-4050-9d28-d349e8e85a1f" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_f199e32b-0960-47e7-a810-b21e37cd3740" xlink:to="loc_srt_SegmentGeographicalDomain_db535229-b2fa-4050-9d28-d349e8e85a1f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_US_0151e501-8028-4885-806a-6cf2dcb4d523" xlink:href="https://xbrl.sec.gov/country/2022/country-2022.xsd#country_US"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_db535229-b2fa-4050-9d28-d349e8e85a1f" xlink:to="loc_country_US_0151e501-8028-4885-806a-6cf2dcb4d523" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_LatinAmericaMember_1bd1dd53-046c-49bb-80d8-27d227bc419d" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_LatinAmericaMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_db535229-b2fa-4050-9d28-d349e8e85a1f" xlink:to="loc_srt_LatinAmericaMember_1bd1dd53-046c-49bb-80d8-27d227bc419d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_OtherCountriesMember_7ed9dcd0-7a1b-4cc4-b83a-ad1107074f29" xlink:href="sncy-20230331.xsd#sncy_OtherCountriesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_db535229-b2fa-4050-9d28-d349e8e85a1f" xlink:to="loc_sncy_OtherCountriesMember_7ed9dcd0-7a1b-4cc4-b83a-ad1107074f29" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.suncountry.com/role/REVENUEContractBalancesDetails" xlink:type="simple" xlink:href="sncy-20230331.xsd#REVENUEContractBalancesDetails"/>
  <link:definitionLink xlink:role="http://www.suncountry.com/role/REVENUEContractBalancesDetails" xlink:type="extended" id="i1d3b862234e340048f1cdd20e1293906_REVENUEContractBalancesDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_b88cb2c0-56ee-4b04-a4ae-d6492456550b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DisaggregationOfRevenueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerAssetNet_2144f2d6-8a4b-4eaf-abe5-6c1b72ade11d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ContractWithCustomerAssetNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_b88cb2c0-56ee-4b04-a4ae-d6492456550b" xlink:to="loc_us-gaap_ContractWithCustomerAssetNet_2144f2d6-8a4b-4eaf-abe5-6c1b72ade11d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiability_983f964b-0fc5-4e1a-930e-85116eb5097c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ContractWithCustomerLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_b88cb2c0-56ee-4b04-a4ae-d6492456550b" xlink:to="loc_us-gaap_ContractWithCustomerLiability_983f964b-0fc5-4e1a-930e-85116eb5097c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_fd079480-8df8-4571-b938-bf0ae92ace8b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DisaggregationOfRevenueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_b88cb2c0-56ee-4b04-a4ae-d6492456550b" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_fd079480-8df8-4571-b938-bf0ae92ace8b" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_e355a8c5-8aa6-4b3c-ac8c-78a90590c3ec" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_fd079480-8df8-4571-b938-bf0ae92ace8b" xlink:to="loc_srt_ProductOrServiceAxis_e355a8c5-8aa6-4b3c-ac8c-78a90590c3ec" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_e355a8c5-8aa6-4b3c-ac8c-78a90590c3ec_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_e355a8c5-8aa6-4b3c-ac8c-78a90590c3ec" xlink:to="loc_srt_ProductsAndServicesDomain_e355a8c5-8aa6-4b3c-ac8c-78a90590c3ec_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_91461015-85d7-4893-9187-ec52eabb7350" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_e355a8c5-8aa6-4b3c-ac8c-78a90590c3ec" xlink:to="loc_srt_ProductsAndServicesDomain_91461015-85d7-4893-9187-ec52eabb7350" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PassengerMember_235bb96f-512c-4743-bf0a-4c01bad0d5bf" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PassengerMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_91461015-85d7-4893-9187-ec52eabb7350" xlink:to="loc_us-gaap_PassengerMember_235bb96f-512c-4743-bf0a-4c01bad0d5bf" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByAssetClassAxis_5c7d2c87-d9a9-40f9-9da4-777809fd4b51" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueByAssetClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_fd079480-8df8-4571-b938-bf0ae92ace8b" xlink:to="loc_us-gaap_FairValueByAssetClassAxis_5c7d2c87-d9a9-40f9-9da4-777809fd4b51" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_5c7d2c87-d9a9-40f9-9da4-777809fd4b51_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByAssetClassAxis_5c7d2c87-d9a9-40f9-9da4-777809fd4b51" xlink:to="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_5c7d2c87-d9a9-40f9-9da4-777809fd4b51_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_2458bb9c-eaaa-43ce-a791-8815cfe6e37b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByAssetClassAxis_5c7d2c87-d9a9-40f9-9da4-777809fd4b51" xlink:to="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_2458bb9c-eaaa-43ce-a791-8815cfe6e37b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_CostsToFulfillContractWithAmazonMember_4fbf76bd-56c0-4b7f-87df-dd0404a8dcde" xlink:href="sncy-20230331.xsd#sncy_CostsToFulfillContractWithAmazonMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_2458bb9c-eaaa-43ce-a791-8815cfe6e37b" xlink:to="loc_sncy_CostsToFulfillContractWithAmazonMember_4fbf76bd-56c0-4b7f-87df-dd0404a8dcde" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByLiabilityClassAxis_a3e5cc0f-ef06-47f7-90fb-cb273f4a6677" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueByLiabilityClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_fd079480-8df8-4571-b938-bf0ae92ace8b" xlink:to="loc_us-gaap_FairValueByLiabilityClassAxis_a3e5cc0f-ef06-47f7-90fb-cb273f4a6677" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_a3e5cc0f-ef06-47f7-90fb-cb273f4a6677_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByLiabilityClassAxis_a3e5cc0f-ef06-47f7-90fb-cb273f4a6677" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_a3e5cc0f-ef06-47f7-90fb-cb273f4a6677_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_76f9a206-864e-464c-ad14-ec1515410244" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByLiabilityClassAxis_a3e5cc0f-ef06-47f7-90fb-cb273f4a6677" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_76f9a206-864e-464c-ad14-ec1515410244" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_AirTrafficLiabilitiesMember_727b74f9-8105-4934-8d5b-283a9af61ceb" xlink:href="sncy-20230331.xsd#sncy_AirTrafficLiabilitiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_76f9a206-864e-464c-ad14-ec1515410244" xlink:to="loc_sncy_AirTrafficLiabilitiesMember_727b74f9-8105-4934-8d5b-283a9af61ceb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_LoyaltyProgramLiabilitiesMember_1708ce5c-1b0b-4564-8981-324e122f0675" xlink:href="sncy-20230331.xsd#sncy_LoyaltyProgramLiabilitiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_76f9a206-864e-464c-ad14-ec1515410244" xlink:to="loc_sncy_LoyaltyProgramLiabilitiesMember_1708ce5c-1b0b-4564-8981-324e122f0675" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_AmazonDeferredStartUpCostsMember_8b4a5805-b54e-49f8-acb9-910862c33871" xlink:href="sncy-20230331.xsd#sncy_AmazonDeferredStartUpCostsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_76f9a206-864e-464c-ad14-ec1515410244" xlink:to="loc_sncy_AmazonDeferredStartUpCostsMember_8b4a5805-b54e-49f8-acb9-910862c33871" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.suncountry.com/role/REVENUEAdditionalInformationDetails" xlink:type="simple" xlink:href="sncy-20230331.xsd#REVENUEAdditionalInformationDetails"/>
  <link:definitionLink xlink:role="http://www.suncountry.com/role/REVENUEAdditionalInformationDetails" xlink:type="extended" id="i45aeb9209be44363b3d7a08587442d37_REVENUEAdditionalInformationDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_36e73e19-23b3-45cd-86c8-cca3364b7151" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiabilityRevenueRecognized_fa4b13c4-6441-4204-92a7-8a7b0fd85a0b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ContractWithCustomerLiabilityRevenueRecognized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_36e73e19-23b3-45cd-86c8-cca3364b7151" xlink:to="loc_us-gaap_ContractWithCustomerLiabilityRevenueRecognized_fa4b13c4-6441-4204-92a7-8a7b0fd85a0b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_1539cca9-63cc-4871-ae8e-b6d1a3977792" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_36e73e19-23b3-45cd-86c8-cca3364b7151" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_1539cca9-63cc-4871-ae8e-b6d1a3977792" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_40e79d39-aeb4-4c7c-88fd-cc2eabd571a7" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_1539cca9-63cc-4871-ae8e-b6d1a3977792" xlink:to="loc_srt_ProductOrServiceAxis_40e79d39-aeb4-4c7c-88fd-cc2eabd571a7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_40e79d39-aeb4-4c7c-88fd-cc2eabd571a7_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_40e79d39-aeb4-4c7c-88fd-cc2eabd571a7" xlink:to="loc_srt_ProductsAndServicesDomain_40e79d39-aeb4-4c7c-88fd-cc2eabd571a7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_1b110f63-03be-4d58-b764-f06215fe6ee2" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_40e79d39-aeb4-4c7c-88fd-cc2eabd571a7" xlink:to="loc_srt_ProductsAndServicesDomain_1b110f63-03be-4d58-b764-f06215fe6ee2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PassengerMember_405a0eec-b3ca-4a95-95fe-f8e7bf125b7b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PassengerMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_1b110f63-03be-4d58-b764-f06215fe6ee2" xlink:to="loc_us-gaap_PassengerMember_405a0eec-b3ca-4a95-95fe-f8e7bf125b7b" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.suncountry.com/role/REVENUELoyaltyProgramDetails" xlink:type="simple" xlink:href="sncy-20230331.xsd#REVENUELoyaltyProgramDetails"/>
  <link:definitionLink xlink:role="http://www.suncountry.com/role/REVENUELoyaltyProgramDetails" xlink:type="extended" id="i45fad0e39be14e2c8d872aa427af0d64_REVENUELoyaltyProgramDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_915a9d1b-76a0-4d69-9c19-2c487ca01917" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DisaggregationOfRevenueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_ChangeInContractWithCustomerLiabilityRollForward_50b638a2-1d8b-4846-ac15-5ea22b6f2078" xlink:href="sncy-20230331.xsd#sncy_ChangeInContractWithCustomerLiabilityRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_915a9d1b-76a0-4d69-9c19-2c487ca01917" xlink:to="loc_sncy_ChangeInContractWithCustomerLiabilityRollForward_50b638a2-1d8b-4846-ac15-5ea22b6f2078" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiability_4e6df19a-14d0-4a30-83a2-16c66abc6b9e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ContractWithCustomerLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_sncy_ChangeInContractWithCustomerLiabilityRollForward_50b638a2-1d8b-4846-ac15-5ea22b6f2078" xlink:to="loc_us-gaap_ContractWithCustomerLiability_4e6df19a-14d0-4a30-83a2-16c66abc6b9e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_ContractWithCustomerLiabilityIncreaseFromLoyaltyPointsEarned_754e263a-150d-42bd-85a9-caa13f15dd1d" xlink:href="sncy-20230331.xsd#sncy_ContractWithCustomerLiabilityIncreaseFromLoyaltyPointsEarned"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_sncy_ChangeInContractWithCustomerLiabilityRollForward_50b638a2-1d8b-4846-ac15-5ea22b6f2078" xlink:to="loc_sncy_ContractWithCustomerLiabilityIncreaseFromLoyaltyPointsEarned_754e263a-150d-42bd-85a9-caa13f15dd1d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiabilityRevenueRecognized_2c2aaa57-5875-41b3-89bd-4ca9bfadf05a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ContractWithCustomerLiabilityRevenueRecognized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_sncy_ChangeInContractWithCustomerLiabilityRollForward_50b638a2-1d8b-4846-ac15-5ea22b6f2078" xlink:to="loc_us-gaap_ContractWithCustomerLiabilityRevenueRecognized_2c2aaa57-5875-41b3-89bd-4ca9bfadf05a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiability_775b19e4-1ed2-48fb-a501-5045a8e75bcb" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ContractWithCustomerLiability"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_d444a1b5-0e60-4eda-9a49-972092352416" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DisaggregationOfRevenueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_915a9d1b-76a0-4d69-9c19-2c487ca01917" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_d444a1b5-0e60-4eda-9a49-972092352416" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByLiabilityClassAxis_1b0bae55-0acc-4284-b295-7e586e00a71e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueByLiabilityClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_d444a1b5-0e60-4eda-9a49-972092352416" xlink:to="loc_us-gaap_FairValueByLiabilityClassAxis_1b0bae55-0acc-4284-b295-7e586e00a71e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_1b0bae55-0acc-4284-b295-7e586e00a71e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByLiabilityClassAxis_1b0bae55-0acc-4284-b295-7e586e00a71e" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_1b0bae55-0acc-4284-b295-7e586e00a71e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_5d27998c-9bf1-49f7-bc9f-dca98c67ca45" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByLiabilityClassAxis_1b0bae55-0acc-4284-b295-7e586e00a71e" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_5d27998c-9bf1-49f7-bc9f-dca98c67ca45" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_LoyaltyProgramLiabilitiesMember_fd883cf9-a400-4177-b040-262a4a701709" xlink:href="sncy-20230331.xsd#sncy_LoyaltyProgramLiabilitiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_5d27998c-9bf1-49f7-bc9f-dca98c67ca45" xlink:to="loc_sncy_LoyaltyProgramLiabilitiesMember_fd883cf9-a400-4177-b040-262a4a701709" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.suncountry.com/role/EARNINGSPERSHAREDetails" xlink:type="simple" xlink:href="sncy-20230331.xsd#EARNINGSPERSHAREDetails"/>
  <link:definitionLink xlink:role="http://www.suncountry.com/role/EARNINGSPERSHAREDetails" xlink:type="extended" id="i91b824522a52415aa568eaeed605fbe7_EARNINGSPERSHAREDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_3a967518-43d1-41b5-b14a-dd7414875b7c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLossAbstract_6f53f299-ff62-42c2-8e87-ddf52e62f545" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_NetIncomeLossAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_3a967518-43d1-41b5-b14a-dd7414875b7c" xlink:to="loc_us-gaap_NetIncomeLossAbstract_6f53f299-ff62-42c2-8e87-ddf52e62f545" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_be23c819-2823-456c-8dcd-fdf58aa6a031" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetIncomeLossAbstract_6f53f299-ff62-42c2-8e87-ddf52e62f545" xlink:to="loc_us-gaap_NetIncomeLoss_be23c819-2823-456c-8dcd-fdf58aa6a031" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_dec33760-45e4-45e2-bd0a-92b684e03037" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_3a967518-43d1-41b5-b14a-dd7414875b7c" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_dec33760-45e4-45e2-bd0a-92b684e03037" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_20cfcfe3-14d1-4ba1-a635-5761afa68421" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_dec33760-45e4-45e2-bd0a-92b684e03037" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_20cfcfe3-14d1-4ba1-a635-5761afa68421" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberDilutedSharesOutstandingAdjustment_cf105079-ce66-43dd-9bce-371065922672" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_WeightedAverageNumberDilutedSharesOutstandingAdjustment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_dec33760-45e4-45e2-bd0a-92b684e03037" xlink:to="loc_us-gaap_WeightedAverageNumberDilutedSharesOutstandingAdjustment_cf105079-ce66-43dd-9bce-371065922672" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_a3fbb291-6cd4-453f-afdc-59700110131f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_dec33760-45e4-45e2-bd0a-92b684e03037" xlink:to="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_a3fbb291-6cd4-453f-afdc-59700110131f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareBasic_fce201df-86bc-49fb-bf99-5d46ba9528e6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EarningsPerShareBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_dec33760-45e4-45e2-bd0a-92b684e03037" xlink:to="loc_us-gaap_EarningsPerShareBasic_fce201df-86bc-49fb-bf99-5d46ba9528e6" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareDiluted_b542c09d-c59d-4986-a3b4-7fdca2800cc0" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EarningsPerShareDiluted"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_dec33760-45e4-45e2-bd0a-92b684e03037" xlink:to="loc_us-gaap_EarningsPerShareDiluted_b542c09d-c59d-4986-a3b4-7fdca2800cc0" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedNumberOfShares_8a934f7b-1a93-445b-9fee-f45a103ddd80" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedNumberOfShares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_3a967518-43d1-41b5-b14a-dd7414875b7c" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedNumberOfShares_8a934f7b-1a93-445b-9fee-f45a103ddd80" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_PercentageOfStockOptionsExpectedToMeetPerformanceConditions_5b748fce-7f7b-40e1-bcde-248a2e71165c" xlink:href="sncy-20230331.xsd#sncy_PercentageOfStockOptionsExpectedToMeetPerformanceConditions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_3a967518-43d1-41b5-b14a-dd7414875b7c" xlink:to="loc_sncy_PercentageOfStockOptionsExpectedToMeetPerformanceConditions_5b748fce-7f7b-40e1-bcde-248a2e71165c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage_a76c2f56-c3b1-4c3a-9bb7-2683fa54073e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_3a967518-43d1-41b5-b14a-dd7414875b7c" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage_a76c2f56-c3b1-4c3a-9bb7-2683fa54073e" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_241181f9-9072-4685-a54f-39786e6e1e1b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_3a967518-43d1-41b5-b14a-dd7414875b7c" xlink:to="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_241181f9-9072-4685-a54f-39786e6e1e1b" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_c74e15d5-4296-4911-be07-0e9968fea065" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_241181f9-9072-4685-a54f-39786e6e1e1b" xlink:to="loc_us-gaap_AwardTypeAxis_c74e15d5-4296-4911-be07-0e9968fea065" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_c74e15d5-4296-4911-be07-0e9968fea065_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_c74e15d5-4296-4911-be07-0e9968fea065" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_c74e15d5-4296-4911-be07-0e9968fea065_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_92b8ad96-3a57-4fe7-805e-5f9cd2c7f47f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_c74e15d5-4296-4911-be07-0e9968fea065" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_92b8ad96-3a57-4fe7-805e-5f9cd2c7f47f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_StockOptionsVestingBasedOnPerformanceMember_beb25215-b64f-4d14-a551-9c503a621e2a" xlink:href="sncy-20230331.xsd#sncy_StockOptionsVestingBasedOnPerformanceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_92b8ad96-3a57-4fe7-805e-5f9cd2c7f47f" xlink:to="loc_sncy_StockOptionsVestingBasedOnPerformanceMember_beb25215-b64f-4d14-a551-9c503a621e2a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_PerformanceBasedStockOptionsMember_09ac2161-951b-4d80-b189-a0252e0e964d" xlink:href="sncy-20230331.xsd#sncy_PerformanceBasedStockOptionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_92b8ad96-3a57-4fe7-805e-5f9cd2c7f47f" xlink:to="loc_sncy_PerformanceBasedStockOptionsMember_09ac2161-951b-4d80-b189-a0252e0e964d" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.suncountry.com/role/AIRCRAFTAdditionalInformationDetails" xlink:type="simple" xlink:href="sncy-20230331.xsd#AIRCRAFTAdditionalInformationDetails"/>
  <link:definitionLink xlink:role="http://www.suncountry.com/role/AIRCRAFTAdditionalInformationDetails" xlink:type="extended" id="i29c11f9ef84c4acb944e47c06955f523_AIRCRAFTAdditionalInformationDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentLineItems_e52c70c6-6ead-4f97-adbf-1c7f40fb45eb" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PropertyPlantAndEquipmentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_PropertyPlantAndEquipmentNumberOfAircraftOutstanding_5d9eacab-4895-490b-acb3-486b0b146e75" xlink:href="sncy-20230331.xsd#sncy_PropertyPlantAndEquipmentNumberOfAircraftOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_e52c70c6-6ead-4f97-adbf-1c7f40fb45eb" xlink:to="loc_sncy_PropertyPlantAndEquipmentNumberOfAircraftOutstanding_5d9eacab-4895-490b-acb3-486b0b146e75" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_PurchaseObligationNumberOfAircraftToBePurchased_1e35c539-5095-404c-a2ac-e53889542f3f" xlink:href="sncy-20230331.xsd#sncy_PurchaseObligationNumberOfAircraftToBePurchased"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_e52c70c6-6ead-4f97-adbf-1c7f40fb45eb" xlink:to="loc_sncy_PurchaseObligationNumberOfAircraftToBePurchased_1e35c539-5095-404c-a2ac-e53889542f3f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_NumberOfAircraftsPurchased_1fa8756a-0b55-4bd6-9530-4d83d3559235" xlink:href="sncy-20230331.xsd#sncy_NumberOfAircraftsPurchased"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_e52c70c6-6ead-4f97-adbf-1c7f40fb45eb" xlink:to="loc_sncy_NumberOfAircraftsPurchased_1fa8756a-0b55-4bd6-9530-4d83d3559235" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_NumberOfAircraftPurchased_f2117f91-72a7-4fae-a886-1b20d863fff6" xlink:href="sncy-20230331.xsd#sncy_NumberOfAircraftPurchased"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_e52c70c6-6ead-4f97-adbf-1c7f40fb45eb" xlink:to="loc_sncy_NumberOfAircraftPurchased_f2117f91-72a7-4fae-a886-1b20d863fff6" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_NumberOfAircraftsFinanced_5ed6fb6e-3323-4a23-a394-0dc0ce7a730e" xlink:href="sncy-20230331.xsd#sncy_NumberOfAircraftsFinanced"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_e52c70c6-6ead-4f97-adbf-1c7f40fb45eb" xlink:to="loc_sncy_NumberOfAircraftsFinanced_5ed6fb6e-3323-4a23-a394-0dc0ce7a730e" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_NumberOfAircraftsUnencumbered_6134ee45-e528-4991-8807-d54644f58640" xlink:href="sncy-20230331.xsd#sncy_NumberOfAircraftsUnencumbered"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_e52c70c6-6ead-4f97-adbf-1c7f40fb45eb" xlink:to="loc_sncy_NumberOfAircraftsUnencumbered_6134ee45-e528-4991-8807-d54644f58640" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_NumberOfAircraftsFinancedUsingProceedsFromIssuanceOfPassThroughTrustCertificates_8492484a-dee8-4c86-8d7a-8add9c1753d7" xlink:href="sncy-20230331.xsd#sncy_NumberOfAircraftsFinancedUsingProceedsFromIssuanceOfPassThroughTrustCertificates"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_e52c70c6-6ead-4f97-adbf-1c7f40fb45eb" xlink:to="loc_sncy_NumberOfAircraftsFinancedUsingProceedsFromIssuanceOfPassThroughTrustCertificates_8492484a-dee8-4c86-8d7a-8add9c1753d7" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_72d4d6a5-5403-4867-beb7-27bc3ee76d23" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfPropertyPlantAndEquipmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_e52c70c6-6ead-4f97-adbf-1c7f40fb45eb" xlink:to="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_72d4d6a5-5403-4867-beb7-27bc3ee76d23" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_AircraftTypeAxis_d4bb9ae3-5ee1-4940-800a-a71a4adb3786" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_AircraftTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_72d4d6a5-5403-4867-beb7-27bc3ee76d23" xlink:to="loc_srt_AircraftTypeAxis_d4bb9ae3-5ee1-4940-800a-a71a4adb3786" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_AircraftTypeMember_d4bb9ae3-5ee1-4940-800a-a71a4adb3786_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_AircraftTypeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_AircraftTypeAxis_d4bb9ae3-5ee1-4940-800a-a71a4adb3786" xlink:to="loc_srt_AircraftTypeMember_d4bb9ae3-5ee1-4940-800a-a71a4adb3786_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_AircraftTypeMember_28bc3592-433e-4fba-ad62-aee508178e75" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_AircraftTypeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_AircraftTypeAxis_d4bb9ae3-5ee1-4940-800a-a71a4adb3786" xlink:to="loc_srt_AircraftTypeMember_28bc3592-433e-4fba-ad62-aee508178e75" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_B737800Member_d60837c4-62fc-4222-afd1-657ed2d92fd2" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_B737800Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_AircraftTypeMember_28bc3592-433e-4fba-ad62-aee508178e75" xlink:to="loc_srt_B737800Member_d60837c4-62fc-4222-afd1-657ed2d92fd2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_B737900Member_f820eb19-4257-4b5b-931a-34d719e2e942" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_B737900Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_AircraftTypeMember_28bc3592-433e-4fba-ad62-aee508178e75" xlink:to="loc_srt_B737900Member_f820eb19-4257-4b5b-931a-34d719e2e942" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_B737700Member_d01acf3c-1e9c-4f58-82df-93092de8cb24" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_B737700Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_AircraftTypeMember_28bc3592-433e-4fba-ad62-aee508178e75" xlink:to="loc_srt_B737700Member_d01acf3c-1e9c-4f58-82df-93092de8cb24" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PassengerMember_949b1d6d-86e0-49a2-8b4a-520b260c3865" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PassengerMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_AircraftTypeMember_28bc3592-433e-4fba-ad62-aee508178e75" xlink:to="loc_us-gaap_PassengerMember_949b1d6d-86e0-49a2-8b4a-520b260c3865" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_f84a13a9-5c5d-417b-baa1-8b9bd39d3e04" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PropertyPlantAndEquipmentByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_72d4d6a5-5403-4867-beb7-27bc3ee76d23" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_f84a13a9-5c5d-417b-baa1-8b9bd39d3e04" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_f84a13a9-5c5d-417b-baa1-8b9bd39d3e04_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_f84a13a9-5c5d-417b-baa1-8b9bd39d3e04" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_f84a13a9-5c5d-417b-baa1-8b9bd39d3e04_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_88108fc7-8085-4113-b9f4-51f081860423" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_f84a13a9-5c5d-417b-baa1-8b9bd39d3e04" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_88108fc7-8085-4113-b9f4-51f081860423" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_AircraftsHeldForOperatingLeaseMember_02d341b6-824e-4095-af79-5c1cffa24a3d" xlink:href="sncy-20230331.xsd#sncy_AircraftsHeldForOperatingLeaseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_88108fc7-8085-4113-b9f4-51f081860423" xlink:to="loc_sncy_AircraftsHeldForOperatingLeaseMember_02d341b6-824e-4095-af79-5c1cffa24a3d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_785b3724-3fa1-4529-b584-923ea4c8a872" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SubsequentEventTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_72d4d6a5-5403-4867-beb7-27bc3ee76d23" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_785b3724-3fa1-4529-b584-923ea4c8a872" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_785b3724-3fa1-4529-b584-923ea4c8a872_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_785b3724-3fa1-4529-b584-923ea4c8a872" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_785b3724-3fa1-4529-b584-923ea4c8a872_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_e2b62b1d-edde-4271-856a-b824d3bc63f1" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_785b3724-3fa1-4529-b584-923ea4c8a872" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_e2b62b1d-edde-4271-856a-b824d3bc63f1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventMember_69acd327-5475-4553-82e9-2ed988fecf90" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SubsequentEventMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_e2b62b1d-edde-4271-856a-b824d3bc63f1" xlink:to="loc_us-gaap_SubsequentEventMember_69acd327-5475-4553-82e9-2ed988fecf90" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetAcquisitionAxis_9a0bed85-fadc-49fd-a689-ed988724be2b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AssetAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_72d4d6a5-5403-4867-beb7-27bc3ee76d23" xlink:to="loc_us-gaap_AssetAcquisitionAxis_9a0bed85-fadc-49fd-a689-ed988724be2b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetAcquisitionDomain_9a0bed85-fadc-49fd-a689-ed988724be2b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AssetAcquisitionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AssetAcquisitionAxis_9a0bed85-fadc-49fd-a689-ed988724be2b" xlink:to="loc_us-gaap_AssetAcquisitionDomain_9a0bed85-fadc-49fd-a689-ed988724be2b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetAcquisitionDomain_d8a53446-beb4-4ecd-bf05-71627c30c555" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AssetAcquisitionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AssetAcquisitionAxis_9a0bed85-fadc-49fd-a689-ed988724be2b" xlink:to="loc_us-gaap_AssetAcquisitionDomain_d8a53446-beb4-4ecd-bf05-71627c30c555" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_AircraftsHeldForOperatingLeaseMember_e946f850-373e-4244-bec0-e9e0fe445453" xlink:href="sncy-20230331.xsd#sncy_AircraftsHeldForOperatingLeaseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetAcquisitionDomain_d8a53446-beb4-4ecd-bf05-71627c30c555" xlink:to="loc_sncy_AircraftsHeldForOperatingLeaseMember_e946f850-373e-4244-bec0-e9e0fe445453" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.suncountry.com/role/AIRCRAFTAircraftFleetDetails" xlink:type="simple" xlink:href="sncy-20230331.xsd#AIRCRAFTAircraftFleetDetails"/>
  <link:definitionLink xlink:role="http://www.suncountry.com/role/AIRCRAFTAircraftFleetDetails" xlink:type="extended" id="i402768b46b8f49f89e6b0ca4dbd8ecf1_AIRCRAFTAircraftFleetDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentLineItems_fcd50993-ce7f-4935-a287-bc1254ca789f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PropertyPlantAndEquipmentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MovementInPropertyPlantAndEquipmentRollForward_82232b36-6164-4bb9-b8d9-83a60dfabb3b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_MovementInPropertyPlantAndEquipmentRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_fcd50993-ce7f-4935-a287-bc1254ca789f" xlink:to="loc_us-gaap_MovementInPropertyPlantAndEquipmentRollForward_82232b36-6164-4bb9-b8d9-83a60dfabb3b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_PropertyPlantAndEquipmentNumberOfAircraftOutstanding_fa65d44b-fe08-44e1-a3a9-e4d52253b21a" xlink:href="sncy-20230331.xsd#sncy_PropertyPlantAndEquipmentNumberOfAircraftOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MovementInPropertyPlantAndEquipmentRollForward_82232b36-6164-4bb9-b8d9-83a60dfabb3b" xlink:to="loc_sncy_PropertyPlantAndEquipmentNumberOfAircraftOutstanding_fa65d44b-fe08-44e1-a3a9-e4d52253b21a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_NumberOfAircraftsPurchased_872ee0ac-826d-42eb-adea-09b4a5cd13a9" xlink:href="sncy-20230331.xsd#sncy_NumberOfAircraftsPurchased"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MovementInPropertyPlantAndEquipmentRollForward_82232b36-6164-4bb9-b8d9-83a60dfabb3b" xlink:to="loc_sncy_NumberOfAircraftsPurchased_872ee0ac-826d-42eb-adea-09b4a5cd13a9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_PropertyPlantAndEquipmentNumberOfAircraftReclassified_a51e98b9-677d-48e3-a37c-30ef55b94f12" xlink:href="sncy-20230331.xsd#sncy_PropertyPlantAndEquipmentNumberOfAircraftReclassified"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MovementInPropertyPlantAndEquipmentRollForward_82232b36-6164-4bb9-b8d9-83a60dfabb3b" xlink:to="loc_sncy_PropertyPlantAndEquipmentNumberOfAircraftReclassified_a51e98b9-677d-48e3-a37c-30ef55b94f12" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentNumberOfAircraftSold_53e05e1a-b248-4b0b-aeea-a4802243d1d3" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PropertyPlantAndEquipmentNumberOfAircraftSold"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MovementInPropertyPlantAndEquipmentRollForward_82232b36-6164-4bb9-b8d9-83a60dfabb3b" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentNumberOfAircraftSold_53e05e1a-b248-4b0b-aeea-a4802243d1d3" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_PropertyPlantAndEquipmentNumberOfAircraftOutstanding_d2cc1e65-ae77-47b9-84c3-926c238b62ce" xlink:href="sncy-20230331.xsd#sncy_PropertyPlantAndEquipmentNumberOfAircraftOutstanding"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_e1ff8127-3ca4-472a-a647-0bee3a515771" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfPropertyPlantAndEquipmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_fcd50993-ce7f-4935-a287-bc1254ca789f" xlink:to="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_e1ff8127-3ca4-472a-a647-0bee3a515771" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_AircraftTypeAxis_e3eeb70c-491b-4586-a930-6faede9ea902" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_AircraftTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_e1ff8127-3ca4-472a-a647-0bee3a515771" xlink:to="loc_srt_AircraftTypeAxis_e3eeb70c-491b-4586-a930-6faede9ea902" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_AircraftTypeMember_e3eeb70c-491b-4586-a930-6faede9ea902_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_AircraftTypeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_AircraftTypeAxis_e3eeb70c-491b-4586-a930-6faede9ea902" xlink:to="loc_srt_AircraftTypeMember_e3eeb70c-491b-4586-a930-6faede9ea902_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_AircraftTypeMember_142c27af-63ef-4583-bf09-54047eb5e047" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_AircraftTypeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_AircraftTypeAxis_e3eeb70c-491b-4586-a930-6faede9ea902" xlink:to="loc_srt_AircraftTypeMember_142c27af-63ef-4583-bf09-54047eb5e047" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PassengerMember_d2276ce0-9d14-452d-b22d-90e47a891c83" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PassengerMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_AircraftTypeMember_142c27af-63ef-4583-bf09-54047eb5e047" xlink:to="loc_us-gaap_PassengerMember_d2276ce0-9d14-452d-b22d-90e47a891c83" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_CargoAircraftMember_ad8639aa-38ab-4d7a-8b2f-0b3f6c9ba998" xlink:href="sncy-20230331.xsd#sncy_CargoAircraftMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_AircraftTypeMember_142c27af-63ef-4583-bf09-54047eb5e047" xlink:to="loc_sncy_CargoAircraftMember_ad8639aa-38ab-4d7a-8b2f-0b3f6c9ba998" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_OtherAircraftMember_a7c9101e-9e56-41c4-b755-26af464203d0" xlink:href="sncy-20230331.xsd#sncy_OtherAircraftMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_AircraftTypeMember_142c27af-63ef-4583-bf09-54047eb5e047" xlink:to="loc_sncy_OtherAircraftMember_a7c9101e-9e56-41c4-b755-26af464203d0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_c94b95b3-0cc3-40dd-a1ac-ec3eb1292008" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PropertyPlantAndEquipmentByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_e1ff8127-3ca4-472a-a647-0bee3a515771" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_c94b95b3-0cc3-40dd-a1ac-ec3eb1292008" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_c94b95b3-0cc3-40dd-a1ac-ec3eb1292008_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_c94b95b3-0cc3-40dd-a1ac-ec3eb1292008" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_c94b95b3-0cc3-40dd-a1ac-ec3eb1292008_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_fda5941b-f020-4b17-b710-eef9a00b2721" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_c94b95b3-0cc3-40dd-a1ac-ec3eb1292008" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_fda5941b-f020-4b17-b710-eef9a00b2721" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_OwnedAircraftsMember_96778ad1-a044-46d5-8062-db55586697ac" xlink:href="sncy-20230331.xsd#sncy_OwnedAircraftsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_fda5941b-f020-4b17-b710-eef9a00b2721" xlink:to="loc_sncy_OwnedAircraftsMember_96778ad1-a044-46d5-8062-db55586697ac" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_AircraftsUnderFinanceLeasesMember_833e99b8-5946-4ada-9862-01a217098f2c" xlink:href="sncy-20230331.xsd#sncy_AircraftsUnderFinanceLeasesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_fda5941b-f020-4b17-b710-eef9a00b2721" xlink:to="loc_sncy_AircraftsUnderFinanceLeasesMember_833e99b8-5946-4ada-9862-01a217098f2c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_AircraftsUnderOperatingLeasesMember_a0bb531c-9b09-4cde-8f99-6ddd1b0753da" xlink:href="sncy-20230331.xsd#sncy_AircraftsUnderOperatingLeasesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_fda5941b-f020-4b17-b710-eef9a00b2721" xlink:to="loc_sncy_AircraftsUnderOperatingLeasesMember_a0bb531c-9b09-4cde-8f99-6ddd1b0753da" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_AircraftsOperatedForAmazonMember_72c0ff88-d318-4401-b1fe-4df80fd71a81" xlink:href="sncy-20230331.xsd#sncy_AircraftsOperatedForAmazonMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_fda5941b-f020-4b17-b710-eef9a00b2721" xlink:to="loc_sncy_AircraftsOperatedForAmazonMember_72c0ff88-d318-4401-b1fe-4df80fd71a81" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_AircraftsHeldForOperatingLeaseMember_fe0af577-b325-4681-a84b-5d94dd7cab50" xlink:href="sncy-20230331.xsd#sncy_AircraftsHeldForOperatingLeaseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_fda5941b-f020-4b17-b710-eef9a00b2721" xlink:to="loc_sncy_AircraftsHeldForOperatingLeaseMember_fe0af577-b325-4681-a84b-5d94dd7cab50" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.suncountry.com/role/AIRCRAFTDepreciationAmortizationandRentExpenseonAircraftDetails" xlink:type="simple" xlink:href="sncy-20230331.xsd#AIRCRAFTDepreciationAmortizationandRentExpenseonAircraftDetails"/>
  <link:definitionLink xlink:role="http://www.suncountry.com/role/AIRCRAFTDepreciationAmortizationandRentExpenseonAircraftDetails" xlink:type="extended" id="ib0001703d79e42b89d81d360680f395b_AIRCRAFTDepreciationAmortizationandRentExpenseonAircraftDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentLineItems_78226769-d3dc-4b25-85ed-a4a6b92cb795" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PropertyPlantAndEquipmentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Depreciation_b649b115-6d1f-4546-80d5-676251e9ba79" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_Depreciation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_78226769-d3dc-4b25-85ed-a4a6b92cb795" xlink:to="loc_us-gaap_Depreciation_b649b115-6d1f-4546-80d5-676251e9ba79" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeaseRightOfUseAssetAmortization_ad0ce9e9-8290-4e0d-b24f-9259421ad592" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinanceLeaseRightOfUseAssetAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_78226769-d3dc-4b25-85ed-a4a6b92cb795" xlink:to="loc_us-gaap_FinanceLeaseRightOfUseAssetAmortization_ad0ce9e9-8290-4e0d-b24f-9259421ad592" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AircraftRental_dc75d442-839f-4bd8-9b56-b1d7f1515729" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AircraftRental"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_78226769-d3dc-4b25-85ed-a4a6b92cb795" xlink:to="loc_us-gaap_AircraftRental_dc75d442-839f-4bd8-9b56-b1d7f1515729" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_DepreciationAmortizationAndRentalExpenses_fdffc1fe-130a-4475-9dad-eb58ccbc366d" xlink:href="sncy-20230331.xsd#sncy_DepreciationAmortizationAndRentalExpenses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_78226769-d3dc-4b25-85ed-a4a6b92cb795" xlink:to="loc_sncy_DepreciationAmortizationAndRentalExpenses_fdffc1fe-130a-4475-9dad-eb58ccbc366d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_92e984fa-5f4a-47a9-950b-745f4fa040a8" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfPropertyPlantAndEquipmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_78226769-d3dc-4b25-85ed-a4a6b92cb795" xlink:to="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_92e984fa-5f4a-47a9-950b-745f4fa040a8" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_e9c81e37-2000-49c9-9406-37e58af42107" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PropertyPlantAndEquipmentByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_92e984fa-5f4a-47a9-950b-745f4fa040a8" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_e9c81e37-2000-49c9-9406-37e58af42107" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_e9c81e37-2000-49c9-9406-37e58af42107_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_e9c81e37-2000-49c9-9406-37e58af42107" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_e9c81e37-2000-49c9-9406-37e58af42107_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_af1f88e2-9cb2-45b4-a5cd-df2c2e05cfad" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_e9c81e37-2000-49c9-9406-37e58af42107" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_af1f88e2-9cb2-45b4-a5cd-df2c2e05cfad" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_OwnedAircraftsMember_1000466c-ff87-4744-a3ee-33b90591b865" xlink:href="sncy-20230331.xsd#sncy_OwnedAircraftsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_af1f88e2-9cb2-45b4-a5cd-df2c2e05cfad" xlink:to="loc_sncy_OwnedAircraftsMember_1000466c-ff87-4744-a3ee-33b90591b865" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_AircraftsUnderFinanceLeasesMember_c7a42d5d-31fc-4da0-9a82-6be4e98d91a5" xlink:href="sncy-20230331.xsd#sncy_AircraftsUnderFinanceLeasesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_af1f88e2-9cb2-45b4-a5cd-df2c2e05cfad" xlink:to="loc_sncy_AircraftsUnderFinanceLeasesMember_c7a42d5d-31fc-4da0-9a82-6be4e98d91a5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_AircraftsUnderOperatingLeasesMember_db0e0104-26e7-4792-9fea-078c39d61a9b" xlink:href="sncy-20230331.xsd#sncy_AircraftsUnderOperatingLeasesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_af1f88e2-9cb2-45b4-a5cd-df2c2e05cfad" xlink:to="loc_sncy_AircraftsUnderOperatingLeasesMember_db0e0104-26e7-4792-9fea-078c39d61a9b" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.suncountry.com/role/ASSETACQUISITIONSAdditionalInformationDetails" xlink:type="simple" xlink:href="sncy-20230331.xsd#ASSETACQUISITIONSAdditionalInformationDetails"/>
  <link:definitionLink xlink:role="http://www.suncountry.com/role/ASSETACQUISITIONSAdditionalInformationDetails" xlink:type="extended" id="iea51b174750b4e1eaf3da6b65411cfc7_ASSETACQUISITIONSAdditionalInformationDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetAcquisitionLineItems_f3e430fd-b196-4079-8230-615a25990016" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AssetAcquisitionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_PurchaseObligationNumberOfAircraftToBePurchased_c39f61d8-016b-4bc7-a957-f53282df4c84" xlink:href="sncy-20230331.xsd#sncy_PurchaseObligationNumberOfAircraftToBePurchased"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetAcquisitionLineItems_f3e430fd-b196-4079-8230-615a25990016" xlink:to="loc_sncy_PurchaseObligationNumberOfAircraftToBePurchased_c39f61d8-016b-4bc7-a957-f53282df4c84" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_NumberOfAircraftsPurchased_39a44dbf-e50d-46b1-af74-6f6e3c910e60" xlink:href="sncy-20230331.xsd#sncy_NumberOfAircraftsPurchased"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetAcquisitionLineItems_f3e430fd-b196-4079-8230-615a25990016" xlink:to="loc_sncy_NumberOfAircraftsPurchased_39a44dbf-e50d-46b1-af74-6f6e3c910e60" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetAcquisitionConsiderationTransferred_562c73bd-ec1d-49d3-b7a3-6fc6e68801ef" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AssetAcquisitionConsiderationTransferred"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetAcquisitionLineItems_f3e430fd-b196-4079-8230-615a25990016" xlink:to="loc_us-gaap_AssetAcquisitionConsiderationTransferred_562c73bd-ec1d-49d3-b7a3-6fc6e68801ef" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_NumberOfAircraftPurchased_1e2cb0f5-b36e-4dd3-9be0-72b5383eef51" xlink:href="sncy-20230331.xsd#sncy_NumberOfAircraftPurchased"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetAcquisitionLineItems_f3e430fd-b196-4079-8230-615a25990016" xlink:to="loc_sncy_NumberOfAircraftPurchased_1e2cb0f5-b36e-4dd3-9be0-72b5383eef51" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCash_e0f38a6d-a1cb-412f-a290-2eeb55e1d421" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RestrictedCash"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetAcquisitionLineItems_f3e430fd-b196-4079-8230-615a25990016" xlink:to="loc_us-gaap_RestrictedCash_e0f38a6d-a1cb-412f-a290-2eeb55e1d421" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFaceAmount_d36b3a14-00cd-4229-8480-05900bc41991" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentFaceAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetAcquisitionLineItems_f3e430fd-b196-4079-8230-615a25990016" xlink:to="loc_us-gaap_DebtInstrumentFaceAmount_d36b3a14-00cd-4229-8480-05900bc41991" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityFairValueOfAmountOutstanding_4cade209-fc49-498d-aab4-baf6aea7cb62" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LineOfCreditFacilityFairValueOfAmountOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetAcquisitionLineItems_f3e430fd-b196-4079-8230-615a25990016" xlink:to="loc_us-gaap_LineOfCreditFacilityFairValueOfAmountOutstanding_4cade209-fc49-498d-aab4-baf6aea7cb62" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LoansAndLeasesReceivableGrossCarryingAmount_10444a2d-e6eb-4414-b452-f0710ee22a33" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LoansAndLeasesReceivableGrossCarryingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetAcquisitionLineItems_f3e430fd-b196-4079-8230-615a25990016" xlink:to="loc_us-gaap_LoansAndLeasesReceivableGrossCarryingAmount_10444a2d-e6eb-4414-b452-f0710ee22a33" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentUsefulLife_f2f8f47d-021a-4e32-afbe-a93156b59f3a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PropertyPlantAndEquipmentUsefulLife"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetAcquisitionLineItems_f3e430fd-b196-4079-8230-615a25990016" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentUsefulLife_f2f8f47d-021a-4e32-afbe-a93156b59f3a" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetAcquisitionTable_22902e6a-0236-41f8-a078-e7689ac42824" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AssetAcquisitionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AssetAcquisitionLineItems_f3e430fd-b196-4079-8230-615a25990016" xlink:to="loc_us-gaap_AssetAcquisitionTable_22902e6a-0236-41f8-a078-e7689ac42824" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_9d90355a-9536-4c37-95fd-a2c4cac5a901" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PropertyPlantAndEquipmentByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_AssetAcquisitionTable_22902e6a-0236-41f8-a078-e7689ac42824" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_9d90355a-9536-4c37-95fd-a2c4cac5a901" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_9d90355a-9536-4c37-95fd-a2c4cac5a901_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_9d90355a-9536-4c37-95fd-a2c4cac5a901" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_9d90355a-9536-4c37-95fd-a2c4cac5a901_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_91e5ec33-4563-4166-b2d7-0db34d3a6ceb" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_9d90355a-9536-4c37-95fd-a2c4cac5a901" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_91e5ec33-4563-4166-b2d7-0db34d3a6ceb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_AircraftsHeldForOperatingLeaseMember_7b48fb32-8858-4943-97aa-9b946fcfec9d" xlink:href="sncy-20230331.xsd#sncy_AircraftsHeldForOperatingLeaseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_91e5ec33-4563-4166-b2d7-0db34d3a6ceb" xlink:to="loc_sncy_AircraftsHeldForOperatingLeaseMember_7b48fb32-8858-4943-97aa-9b946fcfec9d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityAxis_19a35438-a575-46c0-82d6-1e3df5a22c56" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CreditFacilityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_AssetAcquisitionTable_22902e6a-0236-41f8-a078-e7689ac42824" xlink:to="loc_us-gaap_CreditFacilityAxis_19a35438-a575-46c0-82d6-1e3df5a22c56" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_19a35438-a575-46c0-82d6-1e3df5a22c56_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_19a35438-a575-46c0-82d6-1e3df5a22c56" xlink:to="loc_us-gaap_CreditFacilityDomain_19a35438-a575-46c0-82d6-1e3df5a22c56_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_c46cb780-dfdd-438e-974c-561a4aebac78" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_19a35438-a575-46c0-82d6-1e3df5a22c56" xlink:to="loc_us-gaap_CreditFacilityDomain_c46cb780-dfdd-438e-974c-561a4aebac78" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredDebtMember_16972f9b-f593-466a-90dc-aa2c69395afb" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SecuredDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_c46cb780-dfdd-438e-974c-561a4aebac78" xlink:to="loc_us-gaap_SecuredDebtMember_16972f9b-f593-466a-90dc-aa2c69395afb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_a09df171-559d-4345-9dc0-6e979c2a8fad" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_AssetAcquisitionTable_22902e6a-0236-41f8-a078-e7689ac42824" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_a09df171-559d-4345-9dc0-6e979c2a8fad" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_a09df171-559d-4345-9dc0-6e979c2a8fad_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_a09df171-559d-4345-9dc0-6e979c2a8fad" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_a09df171-559d-4345-9dc0-6e979c2a8fad_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_a309892a-c6b1-46b0-89cd-3047cc14f9ac" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_a09df171-559d-4345-9dc0-6e979c2a8fad" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_a309892a-c6b1-46b0-89cd-3047cc14f9ac" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NotesPayableOtherPayablesMember_14f62e53-a28f-47ac-b845-88fecbb15fa8" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_NotesPayableOtherPayablesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_a309892a-c6b1-46b0-89cd-3047cc14f9ac" xlink:to="loc_us-gaap_NotesPayableOtherPayablesMember_14f62e53-a28f-47ac-b845-88fecbb15fa8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_AircraftTypeAxis_503a62b5-8590-453c-ae63-c7d72ef70360" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_AircraftTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_AssetAcquisitionTable_22902e6a-0236-41f8-a078-e7689ac42824" xlink:to="loc_srt_AircraftTypeAxis_503a62b5-8590-453c-ae63-c7d72ef70360" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_AircraftTypeMember_503a62b5-8590-453c-ae63-c7d72ef70360_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_AircraftTypeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_AircraftTypeAxis_503a62b5-8590-453c-ae63-c7d72ef70360" xlink:to="loc_srt_AircraftTypeMember_503a62b5-8590-453c-ae63-c7d72ef70360_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_AircraftTypeMember_2e9fd12f-c2ba-4256-87f3-b49b36748345" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_AircraftTypeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_AircraftTypeAxis_503a62b5-8590-453c-ae63-c7d72ef70360" xlink:to="loc_srt_AircraftTypeMember_2e9fd12f-c2ba-4256-87f3-b49b36748345" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_B737900Member_f323b64a-e10c-4d27-b9cb-e70aaa7569d6" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_B737900Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_AircraftTypeMember_2e9fd12f-c2ba-4256-87f3-b49b36748345" xlink:to="loc_srt_B737900Member_f323b64a-e10c-4d27-b9cb-e70aaa7569d6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_5c991799-9539-41b6-bf3d-603639c269ad" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SubsequentEventTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_AssetAcquisitionTable_22902e6a-0236-41f8-a078-e7689ac42824" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_5c991799-9539-41b6-bf3d-603639c269ad" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_5c991799-9539-41b6-bf3d-603639c269ad_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_5c991799-9539-41b6-bf3d-603639c269ad" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_5c991799-9539-41b6-bf3d-603639c269ad_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_d28f04c1-0b31-4f7e-b969-e06f756031a9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_5c991799-9539-41b6-bf3d-603639c269ad" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_d28f04c1-0b31-4f7e-b969-e06f756031a9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventMember_08088ead-e96d-482e-b390-ca2dac4dcb76" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SubsequentEventMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_d28f04c1-0b31-4f7e-b969-e06f756031a9" xlink:to="loc_us-gaap_SubsequentEventMember_08088ead-e96d-482e-b390-ca2dac4dcb76" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_cba1b662-0712-47a6-9767-2573fe86f248" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_AssetAcquisitionTable_22902e6a-0236-41f8-a078-e7689ac42824" xlink:to="loc_srt_RangeAxis_cba1b662-0712-47a6-9767-2573fe86f248" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_cba1b662-0712-47a6-9767-2573fe86f248_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_cba1b662-0712-47a6-9767-2573fe86f248" xlink:to="loc_srt_RangeMember_cba1b662-0712-47a6-9767-2573fe86f248_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_0dec3de3-a779-4391-a14e-84e70ed353a7" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_cba1b662-0712-47a6-9767-2573fe86f248" xlink:to="loc_srt_RangeMember_0dec3de3-a779-4391-a14e-84e70ed353a7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_65267405-2fc1-469e-9788-24c83a2592ca" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_0dec3de3-a779-4391-a14e-84e70ed353a7" xlink:to="loc_srt_MinimumMember_65267405-2fc1-469e-9788-24c83a2592ca" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_6303b350-e8fe-4238-aefe-db98b3b5ab43" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_0dec3de3-a779-4391-a14e-84e70ed353a7" xlink:to="loc_srt_MaximumMember_6303b350-e8fe-4238-aefe-db98b3b5ab43" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetAcquisitionAxis_153e98a2-dff8-4ae4-a12a-d1cd2ebb6493" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AssetAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_AssetAcquisitionTable_22902e6a-0236-41f8-a078-e7689ac42824" xlink:to="loc_us-gaap_AssetAcquisitionAxis_153e98a2-dff8-4ae4-a12a-d1cd2ebb6493" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetAcquisitionDomain_153e98a2-dff8-4ae4-a12a-d1cd2ebb6493_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AssetAcquisitionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AssetAcquisitionAxis_153e98a2-dff8-4ae4-a12a-d1cd2ebb6493" xlink:to="loc_us-gaap_AssetAcquisitionDomain_153e98a2-dff8-4ae4-a12a-d1cd2ebb6493_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetAcquisitionDomain_53d12bbd-9a1a-4d5a-b26d-b7a7db37771b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AssetAcquisitionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AssetAcquisitionAxis_153e98a2-dff8-4ae4-a12a-d1cd2ebb6493" xlink:to="loc_us-gaap_AssetAcquisitionDomain_53d12bbd-9a1a-4d5a-b26d-b7a7db37771b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_AircraftsHeldForOperatingLeaseMember_7705c817-9770-4dbc-95bb-ee45150f1868" xlink:href="sncy-20230331.xsd#sncy_AircraftsHeldForOperatingLeaseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetAcquisitionDomain_53d12bbd-9a1a-4d5a-b26d-b7a7db37771b" xlink:to="loc_sncy_AircraftsHeldForOperatingLeaseMember_7705c817-9770-4dbc-95bb-ee45150f1868" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_61634059-1a0f-4973-8d8c-765baaa01675" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_AssetAcquisitionTable_22902e6a-0236-41f8-a078-e7689ac42824" xlink:to="loc_us-gaap_DebtInstrumentAxis_61634059-1a0f-4973-8d8c-765baaa01675" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_61634059-1a0f-4973-8d8c-765baaa01675_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_61634059-1a0f-4973-8d8c-765baaa01675" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_61634059-1a0f-4973-8d8c-765baaa01675_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_7c091b88-5c34-4d36-a4e0-c0459ca39107" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_61634059-1a0f-4973-8d8c-765baaa01675" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_7c091b88-5c34-4d36-a4e0-c0459ca39107" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_TermLoanMember_0265d521-2bf2-4a54-9bb3-69f6fc1453a9" xlink:href="sncy-20230331.xsd#sncy_TermLoanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_7c091b88-5c34-4d36-a4e0-c0459ca39107" xlink:to="loc_sncy_TermLoanMember_0265d521-2bf2-4a54-9bb3-69f6fc1453a9" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.suncountry.com/role/ASSETACQUISITIONSAssetAcquisitionDetails" xlink:type="simple" xlink:href="sncy-20230331.xsd#ASSETACQUISITIONSAssetAcquisitionDetails"/>
  <link:definitionLink xlink:role="http://www.suncountry.com/role/ASSETACQUISITIONSAssetAcquisitionDetails" xlink:type="extended" id="ifd96a8f46eb04584ba85512b9e7aa874_ASSETACQUISITIONSAssetAcquisitionDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetAcquisitionLineItems_8d9d396b-4869-46ae-a721-f94ca88459be" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AssetAcquisitionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_AssetAcquisitionAircraftHeldForOperatingLease_682fe643-a6ed-4378-9d74-9826e899fdba" xlink:href="sncy-20230331.xsd#sncy_AssetAcquisitionAircraftHeldForOperatingLease"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetAcquisitionLineItems_8d9d396b-4869-46ae-a721-f94ca88459be" xlink:to="loc_sncy_AssetAcquisitionAircraftHeldForOperatingLease_682fe643-a6ed-4378-9d74-9826e899fdba" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_AssetAcquisitionMaintenanceRightsAsset_42bdf2aa-f077-4f3a-bf89-1a31d171e7f8" xlink:href="sncy-20230331.xsd#sncy_AssetAcquisitionMaintenanceRightsAsset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetAcquisitionLineItems_8d9d396b-4869-46ae-a721-f94ca88459be" xlink:to="loc_sncy_AssetAcquisitionMaintenanceRightsAsset_42bdf2aa-f077-4f3a-bf89-1a31d171e7f8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_AssetAcquisitionOverMarketAsset_d44d7920-d981-4024-81a1-7ce0d2ea8e79" xlink:href="sncy-20230331.xsd#sncy_AssetAcquisitionOverMarketAsset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetAcquisitionLineItems_8d9d396b-4869-46ae-a721-f94ca88459be" xlink:to="loc_sncy_AssetAcquisitionOverMarketAsset_d44d7920-d981-4024-81a1-7ce0d2ea8e79" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_AssetAcquisitionAssetsAcquired_526952ef-ec01-4467-9035-19cc52746912" xlink:href="sncy-20230331.xsd#sncy_AssetAcquisitionAssetsAcquired"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetAcquisitionLineItems_8d9d396b-4869-46ae-a721-f94ca88459be" xlink:to="loc_sncy_AssetAcquisitionAssetsAcquired_526952ef-ec01-4467-9035-19cc52746912" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetAcquisitionTable_40f7fa6d-cab3-41cb-9081-68764b1769bf" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AssetAcquisitionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AssetAcquisitionLineItems_8d9d396b-4869-46ae-a721-f94ca88459be" xlink:to="loc_us-gaap_AssetAcquisitionTable_40f7fa6d-cab3-41cb-9081-68764b1769bf" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_66070085-181d-4dc7-b01c-a0ff06e78171" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PropertyPlantAndEquipmentByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_AssetAcquisitionTable_40f7fa6d-cab3-41cb-9081-68764b1769bf" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_66070085-181d-4dc7-b01c-a0ff06e78171" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_66070085-181d-4dc7-b01c-a0ff06e78171_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_66070085-181d-4dc7-b01c-a0ff06e78171" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_66070085-181d-4dc7-b01c-a0ff06e78171_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_33082ec5-d95e-427b-b6c3-3e6b8d7dde75" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_66070085-181d-4dc7-b01c-a0ff06e78171" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_33082ec5-d95e-427b-b6c3-3e6b8d7dde75" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_AircraftsHeldForOperatingLeaseMember_86acff9c-403f-43fe-b18d-10089ec46fa5" xlink:href="sncy-20230331.xsd#sncy_AircraftsHeldForOperatingLeaseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_33082ec5-d95e-427b-b6c3-3e6b8d7dde75" xlink:to="loc_sncy_AircraftsHeldForOperatingLeaseMember_86acff9c-403f-43fe-b18d-10089ec46fa5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_MaintenanceRightsAssetMember_78f566f6-319b-4a0e-a375-7192587153d1" xlink:href="sncy-20230331.xsd#sncy_MaintenanceRightsAssetMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_33082ec5-d95e-427b-b6c3-3e6b8d7dde75" xlink:to="loc_sncy_MaintenanceRightsAssetMember_78f566f6-319b-4a0e-a375-7192587153d1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_OverMarketAssetMember_b0a21fb4-2874-46f5-b571-faa2b65b3ab5" xlink:href="sncy-20230331.xsd#sncy_OverMarketAssetMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_33082ec5-d95e-427b-b6c3-3e6b8d7dde75" xlink:to="loc_sncy_OverMarketAssetMember_b0a21fb4-2874-46f5-b571-faa2b65b3ab5" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.suncountry.com/role/DEBTCreditFacilitiesDetails" xlink:type="simple" xlink:href="sncy-20230331.xsd#DEBTCreditFacilitiesDetails"/>
  <link:definitionLink xlink:role="http://www.suncountry.com/role/DEBTCreditFacilitiesDetails" xlink:type="extended" id="i716dec0a4018493b9a2139cf21a230fd_DEBTCreditFacilitiesDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_2e90c53a-8308-491a-b8b4-ea6b1711faf4" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTerm_221fd9ab-c923-4258-8f48-423b956a1d15" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2e90c53a-8308-491a-b8b4-ea6b1711faf4" xlink:to="loc_us-gaap_DebtInstrumentTerm_221fd9ab-c923-4258-8f48-423b956a1d15" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_44190b82-b443-4d39-a345-7b9c6e30818d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2e90c53a-8308-491a-b8b4-ea6b1711faf4" xlink:to="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_44190b82-b443-4d39-a345-7b9c6e30818d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_DebtInstrumentFinancialCovenantMinimumEBITDAR_be871999-7d5f-4b09-941d-a1c63a671af0" xlink:href="sncy-20230331.xsd#sncy_DebtInstrumentFinancialCovenantMinimumEBITDAR"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2e90c53a-8308-491a-b8b4-ea6b1711faf4" xlink:to="loc_sncy_DebtInstrumentFinancialCovenantMinimumEBITDAR_be871999-7d5f-4b09-941d-a1c63a671af0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_DebtInstrumentFinancialCovenantMinimumLiquidity_6a47fcda-13f0-4bf3-a601-f5ef2547435a" xlink:href="sncy-20230331.xsd#sncy_DebtInstrumentFinancialCovenantMinimumLiquidity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2e90c53a-8308-491a-b8b4-ea6b1711faf4" xlink:to="loc_sncy_DebtInstrumentFinancialCovenantMinimumLiquidity_6a47fcda-13f0-4bf3-a601-f5ef2547435a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromLinesOfCredit_7d5fa845-d35b-433c-ac97-c4936f8a085b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ProceedsFromLinesOfCredit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2e90c53a-8308-491a-b8b4-ea6b1711faf4" xlink:to="loc_us-gaap_ProceedsFromLinesOfCredit_7d5fa845-d35b-433c-ac97-c4936f8a085b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_NumberOfPurchasedAircraftsPreviouslyUnderOperatingLeases_197371f5-8a79-42db-9dd7-380f34a053fb" xlink:href="sncy-20230331.xsd#sncy_NumberOfPurchasedAircraftsPreviouslyUnderOperatingLeases"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2e90c53a-8308-491a-b8b4-ea6b1711faf4" xlink:to="loc_sncy_NumberOfPurchasedAircraftsPreviouslyUnderOperatingLeases_197371f5-8a79-42db-9dd7-380f34a053fb" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityCurrentBorrowingCapacity_2d806ffb-5a78-41f3-811e-4c2c008331f3" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LineOfCreditFacilityCurrentBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2e90c53a-8308-491a-b8b4-ea6b1711faf4" xlink:to="loc_us-gaap_LineOfCreditFacilityCurrentBorrowingCapacity_2d806ffb-5a78-41f3-811e-4c2c008331f3" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainsLossesOnExtinguishmentOfDebt_617953a4-a78c-4bfa-9e0b-0787a04e4f7d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_GainsLossesOnExtinguishmentOfDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2e90c53a-8308-491a-b8b4-ea6b1711faf4" xlink:to="loc_us-gaap_GainsLossesOnExtinguishmentOfDebt_617953a4-a78c-4bfa-9e0b-0787a04e4f7d" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_LineOfCreditFacilityAmountAvailable_f26aa3d2-1c5d-4ee0-b835-3944776b15db" xlink:href="sncy-20230331.xsd#sncy_LineOfCreditFacilityAmountAvailable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2e90c53a-8308-491a-b8b4-ea6b1711faf4" xlink:to="loc_sncy_LineOfCreditFacilityAmountAvailable_f26aa3d2-1c5d-4ee0-b835-3944776b15db" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentCollateralAmount_6cf3ed78-fb57-4e3e-870c-ba0c19d09eb9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentCollateralAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2e90c53a-8308-491a-b8b4-ea6b1711faf4" xlink:to="loc_us-gaap_DebtInstrumentCollateralAmount_6cf3ed78-fb57-4e3e-870c-ba0c19d09eb9" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_b3ca40eb-20af-4804-a84c-aeb2cba280b6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2e90c53a-8308-491a-b8b4-ea6b1711faf4" xlink:to="loc_us-gaap_DebtInstrumentTable_b3ca40eb-20af-4804-a84c-aeb2cba280b6" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_8ca68e72-c601-42d9-a4a1-3ee53d461c60" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_b3ca40eb-20af-4804-a84c-aeb2cba280b6" xlink:to="loc_us-gaap_DebtInstrumentAxis_8ca68e72-c601-42d9-a4a1-3ee53d461c60" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_8ca68e72-c601-42d9-a4a1-3ee53d461c60_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_8ca68e72-c601-42d9-a4a1-3ee53d461c60" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_8ca68e72-c601-42d9-a4a1-3ee53d461c60_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_927ffb78-a87b-4ed2-8eb7-940fcfc7a977" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_8ca68e72-c601-42d9-a4a1-3ee53d461c60" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_927ffb78-a87b-4ed2-8eb7-940fcfc7a977" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_CreditFacilitiesMember_540a8e7a-d487-4d2c-8cdb-8ec004cbc647" xlink:href="sncy-20230331.xsd#sncy_CreditFacilitiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_927ffb78-a87b-4ed2-8eb7-940fcfc7a977" xlink:to="loc_sncy_CreditFacilitiesMember_540a8e7a-d487-4d2c-8cdb-8ec004cbc647" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_b33f0d61-0451-4810-9d06-ef766b837c8e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RevolvingCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_sncy_CreditFacilitiesMember_540a8e7a-d487-4d2c-8cdb-8ec004cbc647" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_b33f0d61-0451-4810-9d06-ef766b837c8e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_DelayedDrawTermLoanFacilityMember_f332b7d9-32b5-406f-86ad-557091fb8c51" xlink:href="sncy-20230331.xsd#sncy_DelayedDrawTermLoanFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_sncy_CreditFacilitiesMember_540a8e7a-d487-4d2c-8cdb-8ec004cbc647" xlink:to="loc_sncy_DelayedDrawTermLoanFacilityMember_f332b7d9-32b5-406f-86ad-557091fb8c51" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_d99b7a17-1f01-4396-8ca3-85301e74f977" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_b3ca40eb-20af-4804-a84c-aeb2cba280b6" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_d99b7a17-1f01-4396-8ca3-85301e74f977" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_d99b7a17-1f01-4396-8ca3-85301e74f977_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_d99b7a17-1f01-4396-8ca3-85301e74f977" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_d99b7a17-1f01-4396-8ca3-85301e74f977_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_75b2746f-1806-4741-8fdb-22d925a858e3" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_d99b7a17-1f01-4396-8ca3-85301e74f977" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_75b2746f-1806-4741-8fdb-22d925a858e3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditMember_701d50dc-1e4f-4a20-b13a-c8f26de16cbd" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LineOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_75b2746f-1806-4741-8fdb-22d925a858e3" xlink:to="loc_us-gaap_LineOfCreditMember_701d50dc-1e4f-4a20-b13a-c8f26de16cbd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LoansPayableMember_c853ffd0-1d6f-4da4-9e9a-d53297983ec5" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LoansPayableMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_75b2746f-1806-4741-8fdb-22d925a858e3" xlink:to="loc_us-gaap_LoansPayableMember_c853ffd0-1d6f-4da4-9e9a-d53297983ec5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityAxis_025fe454-0dd5-44bd-924b-b0c05848fb6d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CreditFacilityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_b3ca40eb-20af-4804-a84c-aeb2cba280b6" xlink:to="loc_us-gaap_CreditFacilityAxis_025fe454-0dd5-44bd-924b-b0c05848fb6d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_025fe454-0dd5-44bd-924b-b0c05848fb6d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_025fe454-0dd5-44bd-924b-b0c05848fb6d" xlink:to="loc_us-gaap_CreditFacilityDomain_025fe454-0dd5-44bd-924b-b0c05848fb6d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_701bed83-41c2-4710-b045-e3a4df5c09db" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_025fe454-0dd5-44bd-924b-b0c05848fb6d" xlink:to="loc_us-gaap_CreditFacilityDomain_701bed83-41c2-4710-b045-e3a4df5c09db" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_78ef55fd-3e04-4c64-8151-36d315b719bd" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RevolvingCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_701bed83-41c2-4710-b045-e3a4df5c09db" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_78ef55fd-3e04-4c64-8151-36d315b719bd" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.suncountry.com/role/DEBTLongtermDebtDetails" xlink:type="simple" xlink:href="sncy-20230331.xsd#DEBTLongtermDebtDetails"/>
  <link:definitionLink xlink:role="http://www.suncountry.com/role/DEBTLongtermDebtDetails" xlink:type="extended" id="i45fc969209f14d5b9863e45015c94989_DEBTLongtermDebtDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_178cede3-e19d-4437-8a76-457c3ec89b49" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFaceAmount_c52bf6b6-da70-4b26-b986-acc183b19027" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentFaceAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_178cede3-e19d-4437-8a76-457c3ec89b49" xlink:to="loc_us-gaap_DebtInstrumentFaceAmount_c52bf6b6-da70-4b26-b986-acc183b19027" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_NumberOfAircraftHeldForOperatingLease_72de2106-2854-452d-a519-6e35c1bd3a26" xlink:href="sncy-20230331.xsd#sncy_NumberOfAircraftHeldForOperatingLease"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_178cede3-e19d-4437-8a76-457c3ec89b49" xlink:to="loc_sncy_NumberOfAircraftHeldForOperatingLease_72de2106-2854-452d-a519-6e35c1bd3a26" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTerm_a5f83332-8011-4880-bc24-fbf787aa063c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_178cede3-e19d-4437-8a76-457c3ec89b49" xlink:to="loc_us-gaap_DebtInstrumentTerm_a5f83332-8011-4880-bc24-fbf787aa063c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LoansAndLeasesReceivableGrossCarryingAmount_5eae7d92-f8ab-4aa8-92c5-718681ce03a1" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LoansAndLeasesReceivableGrossCarryingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_178cede3-e19d-4437-8a76-457c3ec89b49" xlink:to="loc_us-gaap_LoansAndLeasesReceivableGrossCarryingAmount_5eae7d92-f8ab-4aa8-92c5-718681ce03a1" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_NumberOfAircraftPurchased_2ae5e840-c72c-45f9-b0bd-1e2ece17987f" xlink:href="sncy-20230331.xsd#sncy_NumberOfAircraftPurchased"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_178cede3-e19d-4437-8a76-457c3ec89b49" xlink:to="loc_sncy_NumberOfAircraftPurchased_2ae5e840-c72c-45f9-b0bd-1e2ece17987f" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredFinanceCostsGross_c4fdb5ab-29e0-4e7f-a04f-b5a10fe01385" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DeferredFinanceCostsGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_178cede3-e19d-4437-8a76-457c3ec89b49" xlink:to="loc_us-gaap_DeferredFinanceCostsGross_c4fdb5ab-29e0-4e7f-a04f-b5a10fe01385" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_ac52a11f-0007-406b-a04f-a8c776b4fcaa" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentBasisSpreadOnVariableRate1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_178cede3-e19d-4437-8a76-457c3ec89b49" xlink:to="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_ac52a11f-0007-406b-a04f-a8c776b4fcaa" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_b75af3f5-88c0-49f6-bc06-5d2e454b9884" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_178cede3-e19d-4437-8a76-457c3ec89b49" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_b75af3f5-88c0-49f6-bc06-5d2e454b9884" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_LoanToValueRatio_21d684fa-af4f-4031-a689-0f9933aef493" xlink:href="sncy-20230331.xsd#sncy_LoanToValueRatio"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_178cede3-e19d-4437-8a76-457c3ec89b49" xlink:to="loc_sncy_LoanToValueRatio_21d684fa-af4f-4031-a689-0f9933aef493" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_NumberOfAircraftFinancedByDebtIssuance_4de16d8e-8adf-4f76-9b6a-c556ccedc1cf" xlink:href="sncy-20230331.xsd#sncy_NumberOfAircraftFinancedByDebtIssuance"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_178cede3-e19d-4437-8a76-457c3ec89b49" xlink:to="loc_sncy_NumberOfAircraftFinancedByDebtIssuance_4de16d8e-8adf-4f76-9b6a-c556ccedc1cf" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_NumberOfUsedAircraftsPurchasedOrRefinanced_277092ae-b38a-4973-8800-6b6dc2dbbd64" xlink:href="sncy-20230331.xsd#sncy_NumberOfUsedAircraftsPurchasedOrRefinanced"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_178cede3-e19d-4437-8a76-457c3ec89b49" xlink:to="loc_sncy_NumberOfUsedAircraftsPurchasedOrRefinanced_277092ae-b38a-4973-8800-6b6dc2dbbd64" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityFairValueOfAmountOutstanding_b309eb04-8d75-47ff-9b70-0c71201b5f96" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LineOfCreditFacilityFairValueOfAmountOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_178cede3-e19d-4437-8a76-457c3ec89b49" xlink:to="loc_us-gaap_LineOfCreditFacilityFairValueOfAmountOutstanding_b309eb04-8d75-47ff-9b70-0c71201b5f96" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_NumberOfAircraftsPurchased_85b4e965-4322-479d-9b20-4b96aaeb5929" xlink:href="sncy-20230331.xsd#sncy_NumberOfAircraftsPurchased"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_178cede3-e19d-4437-8a76-457c3ec89b49" xlink:to="loc_sncy_NumberOfAircraftsPurchased_85b4e965-4322-479d-9b20-4b96aaeb5929" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_00394373-a840-4b5a-b7cf-2eee8a450f30" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_178cede3-e19d-4437-8a76-457c3ec89b49" xlink:to="loc_us-gaap_DebtInstrumentTable_00394373-a840-4b5a-b7cf-2eee8a450f30" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_de31142b-1683-430c-9dc0-cee0856a65e2" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_00394373-a840-4b5a-b7cf-2eee8a450f30" xlink:to="loc_us-gaap_DebtInstrumentAxis_de31142b-1683-430c-9dc0-cee0856a65e2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_de31142b-1683-430c-9dc0-cee0856a65e2_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_de31142b-1683-430c-9dc0-cee0856a65e2" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_de31142b-1683-430c-9dc0-cee0856a65e2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_fd5da580-4437-4562-82b6-191e06d7c60f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_de31142b-1683-430c-9dc0-cee0856a65e2" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_fd5da580-4437-4562-82b6-191e06d7c60f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_TermLoanMember_d1d523ad-5356-4ea6-af62-2594305ab4a2" xlink:href="sncy-20230331.xsd#sncy_TermLoanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_fd5da580-4437-4562-82b6-191e06d7c60f" xlink:to="loc_sncy_TermLoanMember_d1d523ad-5356-4ea6-af62-2594305ab4a2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_A20221EETCAgreementNotesPayableMember_e14962dc-0628-4096-b62b-6b39c1df180e" xlink:href="sncy-20230331.xsd#sncy_A20221EETCAgreementNotesPayableMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_fd5da580-4437-4562-82b6-191e06d7c60f" xlink:to="loc_sncy_A20221EETCAgreementNotesPayableMember_e14962dc-0628-4096-b62b-6b39c1df180e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_A20191EETCAgreementNotesPayableMember_056e4dd5-4a3d-40fd-b85c-fc2d83fe864a" xlink:href="sncy-20230331.xsd#sncy_A20191EETCAgreementNotesPayableMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_fd5da580-4437-4562-82b6-191e06d7c60f" xlink:to="loc_sncy_A20191EETCAgreementNotesPayableMember_056e4dd5-4a3d-40fd-b85c-fc2d83fe864a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_5acb53f4-37c4-4d20-831a-d2d38edc9eca" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_00394373-a840-4b5a-b7cf-2eee8a450f30" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_5acb53f4-37c4-4d20-831a-d2d38edc9eca" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_5acb53f4-37c4-4d20-831a-d2d38edc9eca_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_5acb53f4-37c4-4d20-831a-d2d38edc9eca" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_5acb53f4-37c4-4d20-831a-d2d38edc9eca_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_734621ab-0488-437b-84fc-bd1b557065ce" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_5acb53f4-37c4-4d20-831a-d2d38edc9eca" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_734621ab-0488-437b-84fc-bd1b557065ce" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditMember_a545a5c7-ac76-422f-a614-d10842a5327c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LineOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_734621ab-0488-437b-84fc-bd1b557065ce" xlink:to="loc_us-gaap_LineOfCreditMember_a545a5c7-ac76-422f-a614-d10842a5327c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NotesPayableOtherPayablesMember_53e673fe-b210-4ac2-b8ae-73464574877b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_NotesPayableOtherPayablesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_734621ab-0488-437b-84fc-bd1b557065ce" xlink:to="loc_us-gaap_NotesPayableOtherPayablesMember_53e673fe-b210-4ac2-b8ae-73464574877b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_cdb8af81-92e6-4868-9ada-1965d85ba58a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SubsequentEventTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_00394373-a840-4b5a-b7cf-2eee8a450f30" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_cdb8af81-92e6-4868-9ada-1965d85ba58a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_cdb8af81-92e6-4868-9ada-1965d85ba58a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_cdb8af81-92e6-4868-9ada-1965d85ba58a" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_cdb8af81-92e6-4868-9ada-1965d85ba58a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_3e55c787-655d-48e0-935e-c89406342820" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_cdb8af81-92e6-4868-9ada-1965d85ba58a" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_3e55c787-655d-48e0-935e-c89406342820" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventMember_30f0ab95-62d4-4258-8cfb-1273f6ff4d18" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SubsequentEventMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_3e55c787-655d-48e0-935e-c89406342820" xlink:to="loc_us-gaap_SubsequentEventMember_30f0ab95-62d4-4258-8cfb-1273f6ff4d18" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_AircraftTypeAxis_b879e750-cc07-4f17-9e9e-03ebb577b3f9" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_AircraftTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_00394373-a840-4b5a-b7cf-2eee8a450f30" xlink:to="loc_srt_AircraftTypeAxis_b879e750-cc07-4f17-9e9e-03ebb577b3f9" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_AircraftTypeMember_b879e750-cc07-4f17-9e9e-03ebb577b3f9_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_AircraftTypeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_AircraftTypeAxis_b879e750-cc07-4f17-9e9e-03ebb577b3f9" xlink:to="loc_srt_AircraftTypeMember_b879e750-cc07-4f17-9e9e-03ebb577b3f9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_AircraftTypeMember_8c1da344-12d2-43ee-b9f3-25eaff87cbb8" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_AircraftTypeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_AircraftTypeAxis_b879e750-cc07-4f17-9e9e-03ebb577b3f9" xlink:to="loc_srt_AircraftTypeMember_8c1da344-12d2-43ee-b9f3-25eaff87cbb8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_B737900Member_8a33c53d-8f67-4fad-9676-3c1cbf76e549" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_B737900Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_AircraftTypeMember_8c1da344-12d2-43ee-b9f3-25eaff87cbb8" xlink:to="loc_srt_B737900Member_8a33c53d-8f67-4fad-9676-3c1cbf76e549" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityAxis_0d493427-db1d-43f3-a19e-7d1181314232" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CreditFacilityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_00394373-a840-4b5a-b7cf-2eee8a450f30" xlink:to="loc_us-gaap_CreditFacilityAxis_0d493427-db1d-43f3-a19e-7d1181314232" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_0d493427-db1d-43f3-a19e-7d1181314232_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_0d493427-db1d-43f3-a19e-7d1181314232" xlink:to="loc_us-gaap_CreditFacilityDomain_0d493427-db1d-43f3-a19e-7d1181314232_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_c5fdc2d1-79c4-48bc-9af6-ecfda294b501" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_0d493427-db1d-43f3-a19e-7d1181314232" xlink:to="loc_us-gaap_CreditFacilityDomain_c5fdc2d1-79c4-48bc-9af6-ecfda294b501" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredDebtMember_966a4101-565d-4b06-8c11-4f6f4c3ecae7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SecuredDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_c5fdc2d1-79c4-48bc-9af6-ecfda294b501" xlink:to="loc_us-gaap_SecuredDebtMember_966a4101-565d-4b06-8c11-4f6f4c3ecae7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_2bbe61f1-1e51-457a-8c8e-2b9461ae72c1" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_00394373-a840-4b5a-b7cf-2eee8a450f30" xlink:to="loc_srt_RangeAxis_2bbe61f1-1e51-457a-8c8e-2b9461ae72c1" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_2bbe61f1-1e51-457a-8c8e-2b9461ae72c1_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_2bbe61f1-1e51-457a-8c8e-2b9461ae72c1" xlink:to="loc_srt_RangeMember_2bbe61f1-1e51-457a-8c8e-2b9461ae72c1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_04f4a446-5ede-4d5d-8eac-6d1716ebbb6c" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_2bbe61f1-1e51-457a-8c8e-2b9461ae72c1" xlink:to="loc_srt_RangeMember_04f4a446-5ede-4d5d-8eac-6d1716ebbb6c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_97826d4f-3d28-4c2b-803c-781b7f473b21" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_04f4a446-5ede-4d5d-8eac-6d1716ebbb6c" xlink:to="loc_srt_MinimumMember_97826d4f-3d28-4c2b-803c-781b7f473b21" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_acad687c-ba61-43de-b24e-7c340306977c" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_04f4a446-5ede-4d5d-8eac-6d1716ebbb6c" xlink:to="loc_srt_MaximumMember_acad687c-ba61-43de-b24e-7c340306977c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_a813f88c-cbe1-44da-8e18-588b12c55bb5" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PropertyPlantAndEquipmentByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_00394373-a840-4b5a-b7cf-2eee8a450f30" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_a813f88c-cbe1-44da-8e18-588b12c55bb5" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_a813f88c-cbe1-44da-8e18-588b12c55bb5_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_a813f88c-cbe1-44da-8e18-588b12c55bb5" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_a813f88c-cbe1-44da-8e18-588b12c55bb5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_b7ae2add-dd4b-4f5b-bc5f-6fd15a5bf1fb" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_a813f88c-cbe1-44da-8e18-588b12c55bb5" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_b7ae2add-dd4b-4f5b-bc5f-6fd15a5bf1fb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_AircraftsHeldForOperatingLeaseMember_6f85cc24-c3bf-4a2f-bfad-30754e005e2c" xlink:href="sncy-20230331.xsd#sncy_AircraftsHeldForOperatingLeaseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_b7ae2add-dd4b-4f5b-bc5f-6fd15a5bf1fb" xlink:to="loc_sncy_AircraftsHeldForOperatingLeaseMember_6f85cc24-c3bf-4a2f-bfad-30754e005e2c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetAcquisitionAxis_d5441766-e821-4166-a623-5d6881bcc6df" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AssetAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_00394373-a840-4b5a-b7cf-2eee8a450f30" xlink:to="loc_us-gaap_AssetAcquisitionAxis_d5441766-e821-4166-a623-5d6881bcc6df" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetAcquisitionDomain_d5441766-e821-4166-a623-5d6881bcc6df_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AssetAcquisitionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AssetAcquisitionAxis_d5441766-e821-4166-a623-5d6881bcc6df" xlink:to="loc_us-gaap_AssetAcquisitionDomain_d5441766-e821-4166-a623-5d6881bcc6df_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetAcquisitionDomain_3277593e-e4fe-4d7b-b402-7f79488bbcbf" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AssetAcquisitionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AssetAcquisitionAxis_d5441766-e821-4166-a623-5d6881bcc6df" xlink:to="loc_us-gaap_AssetAcquisitionDomain_3277593e-e4fe-4d7b-b402-7f79488bbcbf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_AircraftsHeldForOperatingLeaseMember_3f5262e4-532b-4990-8a79-a91a5b5ac26f" xlink:href="sncy-20230331.xsd#sncy_AircraftsHeldForOperatingLeaseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetAcquisitionDomain_3277593e-e4fe-4d7b-b402-7f79488bbcbf" xlink:to="loc_sncy_AircraftsHeldForOperatingLeaseMember_3f5262e4-532b-4990-8a79-a91a5b5ac26f" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.suncountry.com/role/DEBTLongtermDebtScheduleDetails" xlink:type="simple" xlink:href="sncy-20230331.xsd#DEBTLongtermDebtScheduleDetails"/>
  <link:definitionLink xlink:role="http://www.suncountry.com/role/DEBTLongtermDebtScheduleDetails" xlink:type="extended" id="i6c82213ab58b453da40a388f4893a3f3_DEBTLongtermDebtScheduleDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_29619683-aea4-4d76-8ca0-43334601fa9c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentCarryingAmount_da33f879-07bf-44d8-8cc4-e47e3461391c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentCarryingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_29619683-aea4-4d76-8ca0-43334601fa9c" xlink:to="loc_us-gaap_DebtInstrumentCarryingAmount_da33f879-07bf-44d8-8cc4-e47e3461391c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredFinanceCostsNet_0daf605b-e99d-4afc-9812-21153cb913f8" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DeferredFinanceCostsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_29619683-aea4-4d76-8ca0-43334601fa9c" xlink:to="loc_us-gaap_DeferredFinanceCostsNet_0daf605b-e99d-4afc-9812-21153cb913f8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtCurrent_4584d873-a378-4240-af07-d0f884faee41" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongTermDebtCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_29619683-aea4-4d76-8ca0-43334601fa9c" xlink:to="loc_us-gaap_LongTermDebtCurrent_4584d873-a378-4240-af07-d0f884faee41" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtNoncurrent_fb62c964-9507-49e0-8039-d2cd315049fe" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongTermDebtNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_29619683-aea4-4d76-8ca0-43334601fa9c" xlink:to="loc_us-gaap_LongTermDebtNoncurrent_fb62c964-9507-49e0-8039-d2cd315049fe" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFaceAmount_705bc453-98c4-4d44-b1c3-09f0fdd9abc4" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentFaceAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_29619683-aea4-4d76-8ca0-43334601fa9c" xlink:to="loc_us-gaap_DebtInstrumentFaceAmount_705bc453-98c4-4d44-b1c3-09f0fdd9abc4" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_3549b3ca-9722-49e8-9b72-b270ce23351e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_29619683-aea4-4d76-8ca0-43334601fa9c" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_3549b3ca-9722-49e8-9b72-b270ce23351e" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtWeightedAverageInterestRate_41f7f0bb-20a5-4a49-8d1f-265e4da6ca9e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtWeightedAverageInterestRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_29619683-aea4-4d76-8ca0-43334601fa9c" xlink:to="loc_us-gaap_DebtWeightedAverageInterestRate_41f7f0bb-20a5-4a49-8d1f-265e4da6ca9e" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_54f8a6e5-5d4e-42e6-ac21-8f1cbaf41baa" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_29619683-aea4-4d76-8ca0-43334601fa9c" xlink:to="loc_us-gaap_DebtInstrumentTable_54f8a6e5-5d4e-42e6-ac21-8f1cbaf41baa" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_3b610b1d-c111-4db8-b966-b3ec9bd536db" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_54f8a6e5-5d4e-42e6-ac21-8f1cbaf41baa" xlink:to="loc_us-gaap_DebtInstrumentAxis_3b610b1d-c111-4db8-b966-b3ec9bd536db" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_3b610b1d-c111-4db8-b966-b3ec9bd536db_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_3b610b1d-c111-4db8-b966-b3ec9bd536db" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_3b610b1d-c111-4db8-b966-b3ec9bd536db_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_47370e46-e908-4555-9387-fb5d89adec7a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_3b610b1d-c111-4db8-b966-b3ec9bd536db" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_47370e46-e908-4555-9387-fb5d89adec7a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_A20191EETCAgreementNotesPayableMember_30e1673c-b956-4c11-8529-397b9e385cda" xlink:href="sncy-20230331.xsd#sncy_A20191EETCAgreementNotesPayableMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_47370e46-e908-4555-9387-fb5d89adec7a" xlink:to="loc_sncy_A20191EETCAgreementNotesPayableMember_30e1673c-b956-4c11-8529-397b9e385cda" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_A20221EETCAgreementNotesPayableMember_2f5b5fbd-2445-4cb5-a3d7-b2bda6e00bbc" xlink:href="sncy-20230331.xsd#sncy_A20221EETCAgreementNotesPayableMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_47370e46-e908-4555-9387-fb5d89adec7a" xlink:to="loc_sncy_A20221EETCAgreementNotesPayableMember_2f5b5fbd-2445-4cb5-a3d7-b2bda6e00bbc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_DelayedDrawTermLoanFacilityMember_0abedbed-8f17-41c0-a9e3-f0ab9226244d" xlink:href="sncy-20230331.xsd#sncy_DelayedDrawTermLoanFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_47370e46-e908-4555-9387-fb5d89adec7a" xlink:to="loc_sncy_DelayedDrawTermLoanFacilityMember_0abedbed-8f17-41c0-a9e3-f0ab9226244d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_49996aa2-40cc-4d3b-8926-c246ab5eaa9f" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_54f8a6e5-5d4e-42e6-ac21-8f1cbaf41baa" xlink:to="loc_srt_RangeAxis_49996aa2-40cc-4d3b-8926-c246ab5eaa9f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_49996aa2-40cc-4d3b-8926-c246ab5eaa9f_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_49996aa2-40cc-4d3b-8926-c246ab5eaa9f" xlink:to="loc_srt_RangeMember_49996aa2-40cc-4d3b-8926-c246ab5eaa9f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_7edc429b-592b-4d34-b7d4-ec48ab5e8d1d" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_49996aa2-40cc-4d3b-8926-c246ab5eaa9f" xlink:to="loc_srt_RangeMember_7edc429b-592b-4d34-b7d4-ec48ab5e8d1d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_d82f843f-94c7-4fca-b637-105e67c7d548" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_7edc429b-592b-4d34-b7d4-ec48ab5e8d1d" xlink:to="loc_srt_MinimumMember_d82f843f-94c7-4fca-b637-105e67c7d548" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_19836304-752d-468f-bd46-3903e99c5bab" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_7edc429b-592b-4d34-b7d4-ec48ab5e8d1d" xlink:to="loc_srt_MaximumMember_19836304-752d-468f-bd46-3903e99c5bab" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_c1a5decb-3c17-4475-b923-2c2b2aa31fdd" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_54f8a6e5-5d4e-42e6-ac21-8f1cbaf41baa" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_c1a5decb-3c17-4475-b923-2c2b2aa31fdd" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_c1a5decb-3c17-4475-b923-2c2b2aa31fdd_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_c1a5decb-3c17-4475-b923-2c2b2aa31fdd" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_c1a5decb-3c17-4475-b923-2c2b2aa31fdd_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_fabb0e45-0c04-41b7-a126-4f5dfa4eda34" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_c1a5decb-3c17-4475-b923-2c2b2aa31fdd" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_fabb0e45-0c04-41b7-a126-4f5dfa4eda34" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NotesPayableOtherPayablesMember_18fb658b-3295-4137-b1a3-f422f282193d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_NotesPayableOtherPayablesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_fabb0e45-0c04-41b7-a126-4f5dfa4eda34" xlink:to="loc_us-gaap_NotesPayableOtherPayablesMember_18fb658b-3295-4137-b1a3-f422f282193d" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.suncountry.com/role/InvestmentsDetails" xlink:type="simple" xlink:href="sncy-20230331.xsd#InvestmentsDetails"/>
  <link:definitionLink xlink:role="http://www.suncountry.com/role/InvestmentsDetails" xlink:type="extended" id="if1a2ce94e927474a9aad136fc789fda7_InvestmentsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_3a94378e-53c3-4637-8cf9-06f96c086068" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleAmortizedCostAfterAllowanceForCreditLoss_5be3137c-d982-4af9-b3f5-a5f4dfc21073" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtSecuritiesAvailableForSaleAmortizedCostAfterAllowanceForCreditLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_3a94378e-53c3-4637-8cf9-06f96c086068" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleAmortizedCostAfterAllowanceForCreditLoss_5be3137c-d982-4af9-b3f5-a5f4dfc21073" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax_b4a7bb65-47e3-44dd-8b1e-96b12c652cf4" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_3a94378e-53c3-4637-8cf9-06f96c086068" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax_b4a7bb65-47e3-44dd-8b1e-96b12c652cf4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax_26c78c6d-bacf-4d5a-a8a4-acc6224ac180" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_3a94378e-53c3-4637-8cf9-06f96c086068" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax_26c78c6d-bacf-4d5a-a8a4-acc6224ac180" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_8c954a15-5f9f-4387-a471-be42d423b727" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_3a94378e-53c3-4637-8cf9-06f96c086068" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_8c954a15-5f9f-4387-a471-be42d423b727" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecurities_094d7bd3-d4c3-4d36-a661-088757b8746f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_3a94378e-53c3-4637-8cf9-06f96c086068" xlink:to="loc_us-gaap_DebtSecurities_094d7bd3-d4c3-4d36-a661-088757b8746f" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_4fc539e2-2e58-48f6-a54f-4249155a059d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtSecuritiesAvailableForSaleTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_3a94378e-53c3-4637-8cf9-06f96c086068" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_4fc539e2-2e58-48f6-a54f-4249155a059d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_c6c9f9d8-20bc-4da8-b191-da5a44c72b88" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_4fc539e2-2e58-48f6-a54f-4249155a059d" xlink:to="loc_us-gaap_FinancialInstrumentAxis_c6c9f9d8-20bc-4da8-b191-da5a44c72b88" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_c6c9f9d8-20bc-4da8-b191-da5a44c72b88_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_c6c9f9d8-20bc-4da8-b191-da5a44c72b88" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_c6c9f9d8-20bc-4da8-b191-da5a44c72b88_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_e3d1b229-330a-4859-a582-e4fa3f05f72e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_c6c9f9d8-20bc-4da8-b191-da5a44c72b88" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_e3d1b229-330a-4859-a582-e4fa3f05f72e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesMember_50116b4f-9bbe-4d89-8a9c-f46055c12a26" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_e3d1b229-330a-4859-a582-e4fa3f05f72e" xlink:to="loc_us-gaap_DebtSecuritiesMember_50116b4f-9bbe-4d89-8a9c-f46055c12a26" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateDebtSecuritiesMember_206577b0-fda3-4841-8a30-5cfb9ef2dcd4" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CorporateDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_e3d1b229-330a-4859-a582-e4fa3f05f72e" xlink:to="loc_us-gaap_CorporateDebtSecuritiesMember_206577b0-fda3-4841-8a30-5cfb9ef2dcd4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USGovernmentAgenciesDebtSecuritiesMember_dfb94623-e01c-4395-8331-2bf1d3ad09f9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_USGovernmentAgenciesDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_e3d1b229-330a-4859-a582-e4fa3f05f72e" xlink:to="loc_us-gaap_USGovernmentAgenciesDebtSecuritiesMember_dfb94623-e01c-4395-8331-2bf1d3ad09f9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CertificatesOfDepositMember_cef6fc45-4e42-4a7c-b21b-05896edb997e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CertificatesOfDepositMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_e3d1b229-330a-4859-a582-e4fa3f05f72e" xlink:to="loc_us-gaap_CertificatesOfDepositMember_cef6fc45-4e42-4a7c-b21b-05896edb997e" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.suncountry.com/role/FAIRVALUEMEASUREMENTSDetails" xlink:type="simple" xlink:href="sncy-20230331.xsd#FAIRVALUEMEASUREMENTSDetails"/>
  <link:definitionLink xlink:role="http://www.suncountry.com/role/FAIRVALUEMEASUREMENTSDetails" xlink:type="extended" id="i31b2f027c1f549bd96af842ecc9d1cc6_FAIRVALUEMEASUREMENTSDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_71188b3c-2f76-4b89-b8de-b31e2226fed9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsFairValueDisclosure_9ec6ec53-ee98-487a-9131-9f8b5cfca675" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CashAndCashEquivalentsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_71188b3c-2f76-4b89-b8de-b31e2226fed9" xlink:to="loc_us-gaap_CashAndCashEquivalentsFairValueDisclosure_9ec6ec53-ee98-487a-9131-9f8b5cfca675" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_e6a1d264-ed5e-464d-a700-32669e52de80" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_71188b3c-2f76-4b89-b8de-b31e2226fed9" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_e6a1d264-ed5e-464d-a700-32669e52de80" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsFairValueDisclosure_29fd5f53-e0fe-443e-99ae-3163dd646061" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AssetsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_71188b3c-2f76-4b89-b8de-b31e2226fed9" xlink:to="loc_us-gaap_AssetsFairValueDisclosure_29fd5f53-e0fe-443e-99ae-3163dd646061" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_7f6100fb-b745-4636-b77c-5a5e65ab53c0" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_71188b3c-2f76-4b89-b8de-b31e2226fed9" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_7f6100fb-b745-4636-b77c-5a5e65ab53c0" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByMeasurementFrequencyAxis_ac4e6d68-e285-43bb-865b-a98835548dc9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueByMeasurementFrequencyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_7f6100fb-b745-4636-b77c-5a5e65ab53c0" xlink:to="loc_us-gaap_FairValueByMeasurementFrequencyAxis_ac4e6d68-e285-43bb-865b-a98835548dc9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_ac4e6d68-e285-43bb-865b-a98835548dc9_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueMeasurementFrequencyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_ac4e6d68-e285-43bb-865b-a98835548dc9" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_ac4e6d68-e285-43bb-865b-a98835548dc9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_c33087f1-c89d-4be9-9231-5b7169a4c017" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueMeasurementFrequencyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_ac4e6d68-e285-43bb-865b-a98835548dc9" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_c33087f1-c89d-4be9-9231-5b7169a4c017" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsRecurringMember_45a8dcd2-77f1-4e97-8fb1-db4a4ce402e3" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueMeasurementsRecurringMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementFrequencyDomain_c33087f1-c89d-4be9-9231-5b7169a4c017" xlink:to="loc_us-gaap_FairValueMeasurementsRecurringMember_45a8dcd2-77f1-4e97-8fb1-db4a4ce402e3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_896d476c-4213-47bc-a7ca-d5ce015e656a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_7f6100fb-b745-4636-b77c-5a5e65ab53c0" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_896d476c-4213-47bc-a7ca-d5ce015e656a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_896d476c-4213-47bc-a7ca-d5ce015e656a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_896d476c-4213-47bc-a7ca-d5ce015e656a" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_896d476c-4213-47bc-a7ca-d5ce015e656a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_b4920a55-4cd5-4755-9020-bbefaceb5e30" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_896d476c-4213-47bc-a7ca-d5ce015e656a" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_b4920a55-4cd5-4755-9020-bbefaceb5e30" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_0cebcf64-df33-49f0-a5e3-0aa8478b1d47" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueInputsLevel1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_b4920a55-4cd5-4755-9020-bbefaceb5e30" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_0cebcf64-df33-49f0-a5e3-0aa8478b1d47" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_694dc3f2-14e1-47c0-8c52-7b4fb1d80bb7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueInputsLevel2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_b4920a55-4cd5-4755-9020-bbefaceb5e30" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_694dc3f2-14e1-47c0-8c52-7b4fb1d80bb7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_77549ef6-c8ac-4e26-9b38-ed080bc8d5b1" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueInputsLevel3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_b4920a55-4cd5-4755-9020-bbefaceb5e30" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_77549ef6-c8ac-4e26-9b38-ed080bc8d5b1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_3f7f8382-6c09-4e6f-a5a3-c3c9ae02cbf0" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_7f6100fb-b745-4636-b77c-5a5e65ab53c0" xlink:to="loc_us-gaap_FinancialInstrumentAxis_3f7f8382-6c09-4e6f-a5a3-c3c9ae02cbf0" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_3f7f8382-6c09-4e6f-a5a3-c3c9ae02cbf0_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_3f7f8382-6c09-4e6f-a5a3-c3c9ae02cbf0" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_3f7f8382-6c09-4e6f-a5a3-c3c9ae02cbf0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_9a95228b-e5aa-499f-963b-cff9e2d0e0c7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_3f7f8382-6c09-4e6f-a5a3-c3c9ae02cbf0" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_9a95228b-e5aa-499f-963b-cff9e2d0e0c7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesMember_24e24ae9-411e-4566-bbd1-3769a7073daa" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_9a95228b-e5aa-499f-963b-cff9e2d0e0c7" xlink:to="loc_us-gaap_DebtSecuritiesMember_24e24ae9-411e-4566-bbd1-3769a7073daa" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateDebtSecuritiesMember_6ada1bf4-2c90-4219-8197-32da8b4aa26d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CorporateDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_9a95228b-e5aa-499f-963b-cff9e2d0e0c7" xlink:to="loc_us-gaap_CorporateDebtSecuritiesMember_6ada1bf4-2c90-4219-8197-32da8b4aa26d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USGovernmentAgenciesDebtSecuritiesMember_9847ffbf-8575-4f25-aaac-9506d3049aa0" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_USGovernmentAgenciesDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_9a95228b-e5aa-499f-963b-cff9e2d0e0c7" xlink:to="loc_us-gaap_USGovernmentAgenciesDebtSecuritiesMember_9847ffbf-8575-4f25-aaac-9506d3049aa0" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.suncountry.com/role/STOCKHOLDERSEQUITYDetails" xlink:type="simple" xlink:href="sncy-20230331.xsd#STOCKHOLDERSEQUITYDetails"/>
  <link:definitionLink xlink:role="http://www.suncountry.com/role/STOCKHOLDERSEQUITYDetails" xlink:type="extended" id="i535aefae1a15439986788558bf8132df_STOCKHOLDERSEQUITYDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockLineItems_60982739-a1a0-4496-a684-0654ad1c4e08" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfStockLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_e08fed87-6a48-4238-a15e-2ccf36c9d605" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockIssuedDuringPeriodSharesNewIssues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_60982739-a1a0-4496-a684-0654ad1c4e08" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_e08fed87-6a48-4238-a15e-2ccf36c9d605" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockSharesAcquired_580cd382-20f2-44fa-b0a3-e62c1b336b70" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_TreasuryStockSharesAcquired"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_60982739-a1a0-4496-a684-0654ad1c4e08" xlink:to="loc_us-gaap_TreasuryStockSharesAcquired_580cd382-20f2-44fa-b0a3-e62c1b336b70" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockAcquiredAverageCostPerShare_4cbdb333-5383-425b-9831-b042419714b4" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_TreasuryStockAcquiredAverageCostPerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_60982739-a1a0-4496-a684-0654ad1c4e08" xlink:to="loc_us-gaap_TreasuryStockAcquiredAverageCostPerShare_4cbdb333-5383-425b-9831-b042419714b4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockValueAcquiredCostMethod_76d24127-7175-4cf9-a141-1dbe6de66adc" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_TreasuryStockValueAcquiredCostMethod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_60982739-a1a0-4496-a684-0654ad1c4e08" xlink:to="loc_us-gaap_TreasuryStockValueAcquiredCostMethod_76d24127-7175-4cf9-a141-1dbe6de66adc" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsOfStockIssuanceCosts_94c484c0-f914-4809-9d6a-0559d34c657d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PaymentsOfStockIssuanceCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_60982739-a1a0-4496-a684-0654ad1c4e08" xlink:to="loc_us-gaap_PaymentsOfStockIssuanceCosts_94c484c0-f914-4809-9d6a-0559d34c657d" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchaseProgramAuthorizedAmount1_120ec136-9c9e-4511-b629-b5ef5442fe6b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockRepurchaseProgramAuthorizedAmount1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_60982739-a1a0-4496-a684-0654ad1c4e08" xlink:to="loc_us-gaap_StockRepurchaseProgramAuthorizedAmount1_120ec136-9c9e-4511-b629-b5ef5442fe6b" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchasedDuringPeriodShares_43047f6b-4c60-45a2-83d0-d8aec695c3b0" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockRepurchasedDuringPeriodShares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_60982739-a1a0-4496-a684-0654ad1c4e08" xlink:to="loc_us-gaap_StockRepurchasedDuringPeriodShares_43047f6b-4c60-45a2-83d0-d8aec695c3b0" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AcceleratedShareRepurchasesInitialPricePaidPerShare_76cc0103-4059-4f1d-854e-29a561e1cc9d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AcceleratedShareRepurchasesInitialPricePaidPerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_60982739-a1a0-4496-a684-0654ad1c4e08" xlink:to="loc_us-gaap_AcceleratedShareRepurchasesInitialPricePaidPerShare_76cc0103-4059-4f1d-854e-29a561e1cc9d" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_StocksRepurchasedDuringPeriodSharesTotal_b2cbeec9-dec2-4964-a32a-e9cb1d6baba5" xlink:href="sncy-20230331.xsd#sncy_StocksRepurchasedDuringPeriodSharesTotal"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_60982739-a1a0-4496-a684-0654ad1c4e08" xlink:to="loc_sncy_StocksRepurchasedDuringPeriodSharesTotal_b2cbeec9-dec2-4964-a32a-e9cb1d6baba5" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1_7f43b665-1f63-4ca8-b6b6-db16dfe8029d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_60982739-a1a0-4496-a684-0654ad1c4e08" xlink:to="loc_us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1_7f43b665-1f63-4ca8-b6b6-db16dfe8029d" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_TermOfAgreement_b4ca99c5-ad15-4f68-8b2b-2fe24a24e346" xlink:href="sncy-20230331.xsd#sncy_TermOfAgreement"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_60982739-a1a0-4496-a684-0654ad1c4e08" xlink:to="loc_sncy_TermOfAgreement_b4ca99c5-ad15-4f68-8b2b-2fe24a24e346" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_NumberOfExtensionOptions_669589f6-3f3f-4700-aaa0-b91b58e9eb69" xlink:href="sncy-20230331.xsd#sncy_NumberOfExtensionOptions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_60982739-a1a0-4496-a684-0654ad1c4e08" xlink:to="loc_sncy_NumberOfExtensionOptions_669589f6-3f3f-4700-aaa0-b91b58e9eb69" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_TermOfRenewalOfAgreement_ff02ffc0-e882-4be1-9f68-849c8f9ae18d" xlink:href="sncy-20230331.xsd#sncy_TermOfRenewalOfAgreement"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_60982739-a1a0-4496-a684-0654ad1c4e08" xlink:to="loc_sncy_TermOfRenewalOfAgreement_ff02ffc0-e882-4be1-9f68-849c8f9ae18d" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_ThresholdTermOfAgreement_102d4328-3df2-4c9e-9d50-e22db120670c" xlink:href="sncy-20230331.xsd#sncy_ThresholdTermOfAgreement"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_60982739-a1a0-4496-a684-0654ad1c4e08" xlink:to="loc_sncy_ThresholdTermOfAgreement_102d4328-3df2-4c9e-9d50-e22db120670c" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights_b38f364a-6005-41d7-b8fd-8e81a96f81ef" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_60982739-a1a0-4496-a684-0654ad1c4e08" xlink:to="loc_us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights_b38f364a-6005-41d7-b8fd-8e81a96f81ef" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1_effd7661-afcf-46dc-bf60-489d10fbd289" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_60982739-a1a0-4496-a684-0654ad1c4e08" xlink:to="loc_us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1_effd7661-afcf-46dc-bf60-489d10fbd289" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_WarrantsVestedDuringPeriod_7acdb248-0376-4127-bc42-b6611fe9b34e" xlink:href="sncy-20230331.xsd#sncy_WarrantsVestedDuringPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_60982739-a1a0-4496-a684-0654ad1c4e08" xlink:to="loc_sncy_WarrantsVestedDuringPeriod_7acdb248-0376-4127-bc42-b6611fe9b34e" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_CumulativeWarrantsVested_b8ccba0f-be27-4c26-8f5e-973611373b78" xlink:href="sncy-20230331.xsd#sncy_CumulativeWarrantsVested"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_60982739-a1a0-4496-a684-0654ad1c4e08" xlink:to="loc_sncy_CumulativeWarrantsVested_b8ccba0f-be27-4c26-8f5e-973611373b78" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfStockByClassTable_7e67609f-193c-4705-a66f-70155f192776" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfStockByClassTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ClassOfStockLineItems_60982739-a1a0-4496-a684-0654ad1c4e08" xlink:to="loc_us-gaap_ScheduleOfStockByClassTable_7e67609f-193c-4705-a66f-70155f192776" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareRepurchaseProgramAxis_b02c9ff3-ce7c-4d34-a5f0-8c82bce0e280" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareRepurchaseProgramAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_7e67609f-193c-4705-a66f-70155f192776" xlink:to="loc_us-gaap_ShareRepurchaseProgramAxis_b02c9ff3-ce7c-4d34-a5f0-8c82bce0e280" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareRepurchaseProgramDomain_b02c9ff3-ce7c-4d34-a5f0-8c82bce0e280_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareRepurchaseProgramDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ShareRepurchaseProgramAxis_b02c9ff3-ce7c-4d34-a5f0-8c82bce0e280" xlink:to="loc_us-gaap_ShareRepurchaseProgramDomain_b02c9ff3-ce7c-4d34-a5f0-8c82bce0e280_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareRepurchaseProgramDomain_bb67b9d3-0818-4593-93c8-fe0e98eb44db" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareRepurchaseProgramDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ShareRepurchaseProgramAxis_b02c9ff3-ce7c-4d34-a5f0-8c82bce0e280" xlink:to="loc_us-gaap_ShareRepurchaseProgramDomain_bb67b9d3-0818-4593-93c8-fe0e98eb44db" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_A2022RepurchaseProgramMember_0d11ed21-79c1-49d0-a24c-851e428f2dbc" xlink:href="sncy-20230331.xsd#sncy_A2022RepurchaseProgramMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareRepurchaseProgramDomain_bb67b9d3-0818-4593-93c8-fe0e98eb44db" xlink:to="loc_sncy_A2022RepurchaseProgramMember_0d11ed21-79c1-49d0-a24c-851e428f2dbc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsidiarySaleOfStockAxis_240683a3-005f-493b-a911-85d0d393aef6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SubsidiarySaleOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_7e67609f-193c-4705-a66f-70155f192776" xlink:to="loc_us-gaap_SubsidiarySaleOfStockAxis_240683a3-005f-493b-a911-85d0d393aef6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockNameOfTransactionDomain_240683a3-005f-493b-a911-85d0d393aef6_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SaleOfStockNameOfTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsidiarySaleOfStockAxis_240683a3-005f-493b-a911-85d0d393aef6" xlink:to="loc_us-gaap_SaleOfStockNameOfTransactionDomain_240683a3-005f-493b-a911-85d0d393aef6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockNameOfTransactionDomain_517a192e-d811-4860-9880-5b32433ae3ff" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SaleOfStockNameOfTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsidiarySaleOfStockAxis_240683a3-005f-493b-a911-85d0d393aef6" xlink:to="loc_us-gaap_SaleOfStockNameOfTransactionDomain_517a192e-d811-4860-9880-5b32433ae3ff" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OverAllotmentOptionMember_af246da7-155b-4c00-bdc1-92aa329dab14" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OverAllotmentOptionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SaleOfStockNameOfTransactionDomain_517a192e-d811-4860-9880-5b32433ae3ff" xlink:to="loc_us-gaap_OverAllotmentOptionMember_af246da7-155b-4c00-bdc1-92aa329dab14" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_SecondaryPublicStockOfferingMember_7786297a-89a8-4a65-8705-93d09d1d6a47" xlink:href="sncy-20230331.xsd#sncy_SecondaryPublicStockOfferingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SaleOfStockNameOfTransactionDomain_517a192e-d811-4860-9880-5b32433ae3ff" xlink:to="loc_sncy_SecondaryPublicStockOfferingMember_7786297a-89a8-4a65-8705-93d09d1d6a47" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TypeOfArrangementAxis_319b80f7-b38c-497c-b361-1215c6431c91" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_TypeOfArrangementAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_7e67609f-193c-4705-a66f-70155f192776" xlink:to="loc_us-gaap_TypeOfArrangementAxis_319b80f7-b38c-497c-b361-1215c6431c91" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ArrangementsAndNonarrangementTransactionsMember_319b80f7-b38c-497c-b361-1215c6431c91_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ArrangementsAndNonarrangementTransactionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_TypeOfArrangementAxis_319b80f7-b38c-497c-b361-1215c6431c91" xlink:to="loc_us-gaap_ArrangementsAndNonarrangementTransactionsMember_319b80f7-b38c-497c-b361-1215c6431c91_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ArrangementsAndNonarrangementTransactionsMember_7f0e8167-5714-4770-9480-66c1f6fe4fb0" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ArrangementsAndNonarrangementTransactionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_TypeOfArrangementAxis_319b80f7-b38c-497c-b361-1215c6431c91" xlink:to="loc_us-gaap_ArrangementsAndNonarrangementTransactionsMember_7f0e8167-5714-4770-9480-66c1f6fe4fb0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_AmazonAgreementMember_978661a4-ca4c-4135-9ebd-1b5aad19f182" xlink:href="sncy-20230331.xsd#sncy_AmazonAgreementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ArrangementsAndNonarrangementTransactionsMember_7f0e8167-5714-4770-9480-66c1f6fe4fb0" xlink:to="loc_sncy_AmazonAgreementMember_978661a4-ca4c-4135-9ebd-1b5aad19f182" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.suncountry.com/role/COMMITMENTSANDCONTINGENCIESDetails" xlink:type="simple" xlink:href="sncy-20230331.xsd#COMMITMENTSANDCONTINGENCIESDetails"/>
  <link:definitionLink xlink:role="http://www.suncountry.com/role/COMMITMENTSANDCONTINGENCIESDetails" xlink:type="extended" id="if452e411763b4335a143ee44dd7754b7_COMMITMENTSANDCONTINGENCIESDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermPurchaseCommitmentLineItems_e3bb8863-0250-4986-a663-7d80ebaba412" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongTermPurchaseCommitmentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_NumberOfAircraftToLease_c192e946-e945-4579-b9ca-a63132bcf171" xlink:href="sncy-20230331.xsd#sncy_NumberOfAircraftToLease"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongTermPurchaseCommitmentLineItems_e3bb8863-0250-4986-a663-7d80ebaba412" xlink:to="loc_sncy_NumberOfAircraftToLease_c192e946-e945-4579-b9ca-a63132bcf171" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_fcf99742-283c-4b15-ba88-ccf9e3412d3f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongTermPurchaseCommitmentLineItems_e3bb8863-0250-4986-a663-7d80ebaba412" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_fcf99742-283c-4b15-ba88-ccf9e3412d3f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseTermOfContract_f4333307-cb25-4c92-810a-d94afbf7b35d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LesseeOperatingLeaseTermOfContract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongTermPurchaseCommitmentLineItems_e3bb8863-0250-4986-a663-7d80ebaba412" xlink:to="loc_us-gaap_LesseeOperatingLeaseTermOfContract_f4333307-cb25-4c92-810a-d94afbf7b35d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PurchaseObligation_f0fb7c7b-11e8-42c9-8d46-bf38d2269e53" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PurchaseObligation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongTermPurchaseCommitmentLineItems_e3bb8863-0250-4986-a663-7d80ebaba412" xlink:to="loc_us-gaap_PurchaseObligation_f0fb7c7b-11e8-42c9-8d46-bf38d2269e53" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermPurchaseCommitmentTable_31fe6739-d3d1-4b17-af2f-6049d6b76389" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongTermPurchaseCommitmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LongTermPurchaseCommitmentLineItems_e3bb8863-0250-4986-a663-7d80ebaba412" xlink:to="loc_us-gaap_LongTermPurchaseCommitmentTable_31fe6739-d3d1-4b17-af2f-6049d6b76389" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherCommitmentsAxis_d727b314-b6f2-42e0-a26b-b82fc562ecad" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherCommitmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LongTermPurchaseCommitmentTable_31fe6739-d3d1-4b17-af2f-6049d6b76389" xlink:to="loc_us-gaap_OtherCommitmentsAxis_d727b314-b6f2-42e0-a26b-b82fc562ecad" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherCommitmentsDomain_d727b314-b6f2-42e0-a26b-b82fc562ecad_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherCommitmentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_OtherCommitmentsAxis_d727b314-b6f2-42e0-a26b-b82fc562ecad" xlink:to="loc_us-gaap_OtherCommitmentsDomain_d727b314-b6f2-42e0-a26b-b82fc562ecad_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherCommitmentsDomain_dde4d1c2-cb57-48f2-b6e7-60da7bff519f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherCommitmentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_OtherCommitmentsAxis_d727b314-b6f2-42e0-a26b-b82fc562ecad" xlink:to="loc_us-gaap_OtherCommitmentsDomain_dde4d1c2-cb57-48f2-b6e7-60da7bff519f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommitmentsMember_16995f62-9131-462e-9c37-b33423caf798" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommitmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherCommitmentsDomain_dde4d1c2-cb57-48f2-b6e7-60da7bff519f" xlink:to="loc_us-gaap_CommitmentsMember_16995f62-9131-462e-9c37-b33423caf798" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_137bb53f-e5d5-4c7f-90c2-276ca05bd44b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SubsequentEventTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LongTermPurchaseCommitmentTable_31fe6739-d3d1-4b17-af2f-6049d6b76389" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_137bb53f-e5d5-4c7f-90c2-276ca05bd44b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_137bb53f-e5d5-4c7f-90c2-276ca05bd44b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_137bb53f-e5d5-4c7f-90c2-276ca05bd44b" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_137bb53f-e5d5-4c7f-90c2-276ca05bd44b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_21406ed4-c1de-4187-a8d6-5ff1cade0713" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_137bb53f-e5d5-4c7f-90c2-276ca05bd44b" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_21406ed4-c1de-4187-a8d6-5ff1cade0713" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventMember_f67db975-1a5f-44f2-88b5-dec8316f2cb2" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SubsequentEventMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_21406ed4-c1de-4187-a8d6-5ff1cade0713" xlink:to="loc_us-gaap_SubsequentEventMember_f67db975-1a5f-44f2-88b5-dec8316f2cb2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetAcquisitionAxis_422c180c-8809-4684-8a11-e65ba6c8fe90" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AssetAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LongTermPurchaseCommitmentTable_31fe6739-d3d1-4b17-af2f-6049d6b76389" xlink:to="loc_us-gaap_AssetAcquisitionAxis_422c180c-8809-4684-8a11-e65ba6c8fe90" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetAcquisitionDomain_422c180c-8809-4684-8a11-e65ba6c8fe90_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AssetAcquisitionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AssetAcquisitionAxis_422c180c-8809-4684-8a11-e65ba6c8fe90" xlink:to="loc_us-gaap_AssetAcquisitionDomain_422c180c-8809-4684-8a11-e65ba6c8fe90_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetAcquisitionDomain_a7d08106-0c13-4da9-84f4-88aa641b994e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AssetAcquisitionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AssetAcquisitionAxis_422c180c-8809-4684-8a11-e65ba6c8fe90" xlink:to="loc_us-gaap_AssetAcquisitionDomain_a7d08106-0c13-4da9-84f4-88aa641b994e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_AircraftsHeldForOperatingLeaseMember_681af6e8-d3f0-4773-8016-f7b8b9e24551" xlink:href="sncy-20230331.xsd#sncy_AircraftsHeldForOperatingLeaseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetAcquisitionDomain_a7d08106-0c13-4da9-84f4-88aa641b994e" xlink:to="loc_sncy_AircraftsHeldForOperatingLeaseMember_681af6e8-d3f0-4773-8016-f7b8b9e24551" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermPurchaseCommitmentByCategoryOfItemPurchasedAxis_78d27b6f-6f62-4d54-8e5d-63cca2532642" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongTermPurchaseCommitmentByCategoryOfItemPurchasedAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LongTermPurchaseCommitmentTable_31fe6739-d3d1-4b17-af2f-6049d6b76389" xlink:to="loc_us-gaap_LongTermPurchaseCommitmentByCategoryOfItemPurchasedAxis_78d27b6f-6f62-4d54-8e5d-63cca2532642" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermPurchaseCommitmentCategoryOfItemPurchasedDomain_78d27b6f-6f62-4d54-8e5d-63cca2532642_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongTermPurchaseCommitmentCategoryOfItemPurchasedDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongTermPurchaseCommitmentByCategoryOfItemPurchasedAxis_78d27b6f-6f62-4d54-8e5d-63cca2532642" xlink:to="loc_us-gaap_LongTermPurchaseCommitmentCategoryOfItemPurchasedDomain_78d27b6f-6f62-4d54-8e5d-63cca2532642_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermPurchaseCommitmentCategoryOfItemPurchasedDomain_1f7b2e64-5df3-4361-8f8f-df705d18f20d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongTermPurchaseCommitmentCategoryOfItemPurchasedDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongTermPurchaseCommitmentByCategoryOfItemPurchasedAxis_78d27b6f-6f62-4d54-8e5d-63cca2532642" xlink:to="loc_us-gaap_LongTermPurchaseCommitmentCategoryOfItemPurchasedDomain_1f7b2e64-5df3-4361-8f8f-df705d18f20d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_IncrementalAircraftMember_54010e3e-01f2-4b22-9d67-afe7d431dbaa" xlink:href="sncy-20230331.xsd#sncy_IncrementalAircraftMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongTermPurchaseCommitmentCategoryOfItemPurchasedDomain_1f7b2e64-5df3-4361-8f8f-df705d18f20d" xlink:to="loc_sncy_IncrementalAircraftMember_54010e3e-01f2-4b22-9d67-afe7d431dbaa" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.suncountry.com/role/OPERATINGSEGMENTSDetails" xlink:type="simple" xlink:href="sncy-20230331.xsd#OPERATINGSEGMENTSDetails"/>
  <link:definitionLink xlink:role="http://www.suncountry.com/role/OPERATINGSEGMENTSDetails" xlink:type="extended" id="if0f515f95fe944a095d298616691b6fe_OPERATINGSEGMENTSDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_73dcb861-4c75-495d-b065-64b2e382b271" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NumberOfOperatingSegments_1e0d9fe5-d0ec-4c7d-a58c-34711e4189a2" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_NumberOfOperatingSegments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_73dcb861-4c75-495d-b065-64b2e382b271" xlink:to="loc_us-gaap_NumberOfOperatingSegments_1e0d9fe5-d0ec-4c7d-a58c-34711e4189a2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_d4a80db2-29f1-40f2-8351-b304d9bdbed7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_73dcb861-4c75-495d-b065-64b2e382b271" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_d4a80db2-29f1-40f2-8351-b304d9bdbed7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_NonFuelOperatingExpenses_446d06d8-ce26-4ede-bee8-43278459e057" xlink:href="sncy-20230331.xsd#sncy_NonFuelOperatingExpenses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_73dcb861-4c75-495d-b065-64b2e382b271" xlink:to="loc_sncy_NonFuelOperatingExpenses_446d06d8-ce26-4ede-bee8-43278459e057" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FuelCosts_dfa2c1bf-0566-4da8-a0d8-193a745c2bee" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FuelCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_73dcb861-4c75-495d-b065-64b2e382b271" xlink:to="loc_us-gaap_FuelCosts_dfa2c1bf-0566-4da8-a0d8-193a745c2bee" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostsAndExpenses_c785a4fc-e21b-426f-af66-cb044de08d4f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CostsAndExpenses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_73dcb861-4c75-495d-b065-64b2e382b271" xlink:to="loc_us-gaap_CostsAndExpenses_c785a4fc-e21b-426f-af66-cb044de08d4f" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingIncomeLoss_7bef28ec-31af-4b8e-ab41-29b73a3117f5" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OperatingIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_73dcb861-4c75-495d-b065-64b2e382b271" xlink:to="loc_us-gaap_OperatingIncomeLoss_7bef28ec-31af-4b8e-ab41-29b73a3117f5" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentIncomeInterest_7e72e836-239c-4112-9bae-be7be9c0bb83" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_InvestmentIncomeInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_73dcb861-4c75-495d-b065-64b2e382b271" xlink:to="loc_us-gaap_InvestmentIncomeInterest_7e72e836-239c-4112-9bae-be7be9c0bb83" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpense_f496625d-ee88-4bb9-a0f8-2b8f0c3a7c54" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_InterestExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_73dcb861-4c75-495d-b065-64b2e382b271" xlink:to="loc_us-gaap_InterestExpense_f496625d-ee88-4bb9-a0f8-2b8f0c3a7c54" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherNonoperatingIncomeExpense_27cbf7d5-4506-4a0b-a6a9-759c93e6ac7f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherNonoperatingIncomeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_73dcb861-4c75-495d-b065-64b2e382b271" xlink:to="loc_us-gaap_OtherNonoperatingIncomeExpense_27cbf7d5-4506-4a0b-a6a9-759c93e6ac7f" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_8989a5ff-31cf-44b8-8bd2-2ec26869dce6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_73dcb861-4c75-495d-b065-64b2e382b271" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_8989a5ff-31cf-44b8-8bd2-2ec26869dce6" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_419f8707-2347-4ebd-a499-0b1f01d3f449" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_73dcb861-4c75-495d-b065-64b2e382b271" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_419f8707-2347-4ebd-a499-0b1f01d3f449" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_e93ec7ae-f542-4382-9fa0-eeba6c926329" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_419f8707-2347-4ebd-a499-0b1f01d3f449" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_e93ec7ae-f542-4382-9fa0-eeba6c926329" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_e93ec7ae-f542-4382-9fa0-eeba6c926329_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_e93ec7ae-f542-4382-9fa0-eeba6c926329" xlink:to="loc_us-gaap_SegmentDomain_e93ec7ae-f542-4382-9fa0-eeba6c926329_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_ae67aa3b-faf7-4095-ae6c-11b09ed2dec5" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_e93ec7ae-f542-4382-9fa0-eeba6c926329" xlink:to="loc_us-gaap_SegmentDomain_ae67aa3b-faf7-4095-ae6c-11b09ed2dec5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_PassengerSegmentMember_31b69bd1-801c-427f-8ffe-bad3d8490863" xlink:href="sncy-20230331.xsd#sncy_PassengerSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_ae67aa3b-faf7-4095-ae6c-11b09ed2dec5" xlink:to="loc_sncy_PassengerSegmentMember_31b69bd1-801c-427f-8ffe-bad3d8490863" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_CargoSegmentMember_afa21ad6-064c-4126-8d79-ff5a6dee3531" xlink:href="sncy-20230331.xsd#sncy_CargoSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_ae67aa3b-faf7-4095-ae6c-11b09ed2dec5" xlink:to="loc_sncy_CargoSegmentMember_afa21ad6-064c-4126-8d79-ff5a6dee3531" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.suncountry.com/role/SUBSEQUENTEVENTSDetails" xlink:type="simple" xlink:href="sncy-20230331.xsd#SUBSEQUENTEVENTSDetails"/>
  <link:definitionLink xlink:role="http://www.suncountry.com/role/SUBSEQUENTEVENTSDetails" xlink:type="extended" id="ica23e1c60e6b4b16a410494c2d15052f_SUBSEQUENTEVENTSDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventLineItems_d2d243d4-196c-4fc6-b537-167d0320d667" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SubsequentEventLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_PurchaseObligationNumberOfAircraftToBePurchased_437cb3bf-4e86-4592-9b8a-ce7b36f1db0b" xlink:href="sncy-20230331.xsd#sncy_PurchaseObligationNumberOfAircraftToBePurchased"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_d2d243d4-196c-4fc6-b537-167d0320d667" xlink:to="loc_sncy_PurchaseObligationNumberOfAircraftToBePurchased_437cb3bf-4e86-4592-9b8a-ce7b36f1db0b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_NumberOfAircraftPurchased_21ba9183-8e00-4230-bb3f-5d492c455c34" xlink:href="sncy-20230331.xsd#sncy_NumberOfAircraftPurchased"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_d2d243d4-196c-4fc6-b537-167d0320d667" xlink:to="loc_sncy_NumberOfAircraftPurchased_21ba9183-8e00-4230-bb3f-5d492c455c34" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetAcquisitionConsiderationTransferred_82f18086-6a9c-41c1-a776-f3728853160b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AssetAcquisitionConsiderationTransferred"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_d2d243d4-196c-4fc6-b537-167d0320d667" xlink:to="loc_us-gaap_AssetAcquisitionConsiderationTransferred_82f18086-6a9c-41c1-a776-f3728853160b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LoansAndLeasesReceivableGrossCarryingAmount_0f2f87ed-f938-47f4-ad1c-2271a94c87a5" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LoansAndLeasesReceivableGrossCarryingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_d2d243d4-196c-4fc6-b537-167d0320d667" xlink:to="loc_us-gaap_LoansAndLeasesReceivableGrossCarryingAmount_0f2f87ed-f938-47f4-ad1c-2271a94c87a5" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCash_50ec5215-0512-4f4a-84af-85f51915400b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RestrictedCash"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_d2d243d4-196c-4fc6-b537-167d0320d667" xlink:to="loc_us-gaap_RestrictedCash_50ec5215-0512-4f4a-84af-85f51915400b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTable_42241ca2-2f4c-48ef-b037-42217ffce04c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SubsequentEventTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SubsequentEventLineItems_d2d243d4-196c-4fc6-b537-167d0320d667" xlink:to="loc_us-gaap_SubsequentEventTable_42241ca2-2f4c-48ef-b037-42217ffce04c" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_5ac1adc4-b22c-49c9-b1b5-b359e0a5c19e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SubsequentEventTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_42241ca2-2f4c-48ef-b037-42217ffce04c" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_5ac1adc4-b22c-49c9-b1b5-b359e0a5c19e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_5ac1adc4-b22c-49c9-b1b5-b359e0a5c19e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_5ac1adc4-b22c-49c9-b1b5-b359e0a5c19e" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_5ac1adc4-b22c-49c9-b1b5-b359e0a5c19e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_e7359a01-0861-4761-a671-c96bdd96f157" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_5ac1adc4-b22c-49c9-b1b5-b359e0a5c19e" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_e7359a01-0861-4761-a671-c96bdd96f157" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventMember_c75216c9-e60a-4ac6-a2fa-ecd170816b41" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SubsequentEventMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_e7359a01-0861-4761-a671-c96bdd96f157" xlink:to="loc_us-gaap_SubsequentEventMember_c75216c9-e60a-4ac6-a2fa-ecd170816b41" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetAcquisitionAxis_6e3c7192-cc6c-40e5-b610-e7c48c8c065a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AssetAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_42241ca2-2f4c-48ef-b037-42217ffce04c" xlink:to="loc_us-gaap_AssetAcquisitionAxis_6e3c7192-cc6c-40e5-b610-e7c48c8c065a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetAcquisitionDomain_6e3c7192-cc6c-40e5-b610-e7c48c8c065a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AssetAcquisitionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AssetAcquisitionAxis_6e3c7192-cc6c-40e5-b610-e7c48c8c065a" xlink:to="loc_us-gaap_AssetAcquisitionDomain_6e3c7192-cc6c-40e5-b610-e7c48c8c065a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetAcquisitionDomain_54f91bee-ca71-4692-90ce-3822de76872a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AssetAcquisitionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AssetAcquisitionAxis_6e3c7192-cc6c-40e5-b610-e7c48c8c065a" xlink:to="loc_us-gaap_AssetAcquisitionDomain_54f91bee-ca71-4692-90ce-3822de76872a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_AircraftsHeldForOperatingLeaseMember_ddb717d6-21f6-44df-847b-d8145489f87b" xlink:href="sncy-20230331.xsd#sncy_AircraftsHeldForOperatingLeaseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetAcquisitionDomain_54f91bee-ca71-4692-90ce-3822de76872a" xlink:to="loc_sncy_AircraftsHeldForOperatingLeaseMember_ddb717d6-21f6-44df-847b-d8145489f87b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_AircraftTypeAxis_da758185-fa26-4b0c-8270-c0847dc9eba9" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_AircraftTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_42241ca2-2f4c-48ef-b037-42217ffce04c" xlink:to="loc_srt_AircraftTypeAxis_da758185-fa26-4b0c-8270-c0847dc9eba9" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_AircraftTypeMember_da758185-fa26-4b0c-8270-c0847dc9eba9_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_AircraftTypeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_AircraftTypeAxis_da758185-fa26-4b0c-8270-c0847dc9eba9" xlink:to="loc_srt_AircraftTypeMember_da758185-fa26-4b0c-8270-c0847dc9eba9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_AircraftTypeMember_d6ece8d8-f10b-43a0-ba21-a95184c2fe8e" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_AircraftTypeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_AircraftTypeAxis_da758185-fa26-4b0c-8270-c0847dc9eba9" xlink:to="loc_srt_AircraftTypeMember_d6ece8d8-f10b-43a0-ba21-a95184c2fe8e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_B737900Member_3f6cb922-521c-42be-ad45-9a9701155a4e" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_B737900Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_AircraftTypeMember_d6ece8d8-f10b-43a0-ba21-a95184c2fe8e" xlink:to="loc_srt_B737900Member_3f6cb922-521c-42be-ad45-9a9701155a4e" xlink:type="arc" order="0"/>
  </link:definitionLink>
</link:linkbase>
