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

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2025 Workiva-->
<!--r:a571028c-4978-4225-93c9-a524b71d731f,g:612bb43a-fa99-4837-a53b-b9604092bd55-->
<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/Cover" xlink:type="simple" xlink:href="sncy-20250501.xsd#Cover"/>
  <link:definitionLink xlink:role="http://www.suncountry.com/role/Cover" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityInformationLineItems_7347df24-5a6a-4cd9-8a6a-defe94a094ac" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_EntityInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntitiesTable_39b5e61d-c579-454c-82d9-5433780a7ed9" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_EntitiesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_dei_EntityInformationLineItems_7347df24-5a6a-4cd9-8a6a-defe94a094ac" xlink:to="loc_dei_EntitiesTable_39b5e61d-c579-454c-82d9-5433780a7ed9" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityListingsExchangeAxis_bb8ade06-f814-4d75-bbf9-2993766ba0f8" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_EntityListingsExchangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_dei_EntitiesTable_39b5e61d-c579-454c-82d9-5433780a7ed9" xlink:to="loc_dei_EntityListingsExchangeAxis_bb8ade06-f814-4d75-bbf9-2993766ba0f8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_ExchangeDomain_bb8ade06-f814-4d75-bbf9-2993766ba0f8_default" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_ExchangeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_EntityListingsExchangeAxis_bb8ade06-f814-4d75-bbf9-2993766ba0f8" xlink:to="loc_dei_ExchangeDomain_bb8ade06-f814-4d75-bbf9-2993766ba0f8_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_ExchangeDomain_13871027-94f2-4959-a5e8-1b4a41664851" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_ExchangeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_EntityListingsExchangeAxis_bb8ade06-f814-4d75-bbf9-2993766ba0f8" xlink:to="loc_dei_ExchangeDomain_13871027-94f2-4959-a5e8-1b4a41664851" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_TheNasdaqStockMarketLLCMember_7bcf188a-bd8a-41dd-9a9c-b06b4d5d8c22" xlink:href="sncy-20250501.xsd#sncy_TheNasdaqStockMarketLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_ExchangeDomain_13871027-94f2-4959-a5e8-1b4a41664851" xlink:to="loc_sncy_TheNasdaqStockMarketLLCMember_7bcf188a-bd8a-41dd-9a9c-b06b4d5d8c22" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentType_00540b18-1a46-4dd8-b058-f2efaf1f689a" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_DocumentType"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_7347df24-5a6a-4cd9-8a6a-defe94a094ac" xlink:to="loc_dei_DocumentType_00540b18-1a46-4dd8-b058-f2efaf1f689a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentPeriodEndDate_241dc30f-10be-4c6d-a1d7-db2c29e177b4" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_DocumentPeriodEndDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_7347df24-5a6a-4cd9-8a6a-defe94a094ac" xlink:to="loc_dei_DocumentPeriodEndDate_241dc30f-10be-4c6d-a1d7-db2c29e177b4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityRegistrantName_b704d6b2-20d1-47da-9ad8-8dcd66845a68" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_EntityRegistrantName"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_7347df24-5a6a-4cd9-8a6a-defe94a094ac" xlink:to="loc_dei_EntityRegistrantName_b704d6b2-20d1-47da-9ad8-8dcd66845a68" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityIncorporationStateCountryCode_29288d34-53ac-4123-951e-9e6bcb25b3d7" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_EntityIncorporationStateCountryCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_7347df24-5a6a-4cd9-8a6a-defe94a094ac" xlink:to="loc_dei_EntityIncorporationStateCountryCode_29288d34-53ac-4123-951e-9e6bcb25b3d7" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityFileNumber_685dd1e6-d186-4364-96f3-fbdeccf6e123" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_EntityFileNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_7347df24-5a6a-4cd9-8a6a-defe94a094ac" xlink:to="loc_dei_EntityFileNumber_685dd1e6-d186-4364-96f3-fbdeccf6e123" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityTaxIdentificationNumber_869c2434-c402-4391-a08e-ae32ddae952e" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_EntityTaxIdentificationNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_7347df24-5a6a-4cd9-8a6a-defe94a094ac" xlink:to="loc_dei_EntityTaxIdentificationNumber_869c2434-c402-4391-a08e-ae32ddae952e" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressAddressLine1_87909239-5a70-4dc4-9366-ffa89801e6b7" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_EntityAddressAddressLine1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_7347df24-5a6a-4cd9-8a6a-defe94a094ac" xlink:to="loc_dei_EntityAddressAddressLine1_87909239-5a70-4dc4-9366-ffa89801e6b7" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressCityOrTown_c8fc7e17-6409-49df-ae75-18977ce4efd7" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_EntityAddressCityOrTown"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_7347df24-5a6a-4cd9-8a6a-defe94a094ac" xlink:to="loc_dei_EntityAddressCityOrTown_c8fc7e17-6409-49df-ae75-18977ce4efd7" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressStateOrProvince_354b2ffb-31cd-4569-ae63-e5841da08ee2" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_EntityAddressStateOrProvince"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_7347df24-5a6a-4cd9-8a6a-defe94a094ac" xlink:to="loc_dei_EntityAddressStateOrProvince_354b2ffb-31cd-4569-ae63-e5841da08ee2" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressPostalZipCode_31bd3359-9eb6-4235-823e-3e03e43bf7a1" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_EntityAddressPostalZipCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_7347df24-5a6a-4cd9-8a6a-defe94a094ac" xlink:to="loc_dei_EntityAddressPostalZipCode_31bd3359-9eb6-4235-823e-3e03e43bf7a1" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_CityAreaCode_ddde9449-31a2-423f-a138-bf481818c557" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_CityAreaCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_7347df24-5a6a-4cd9-8a6a-defe94a094ac" xlink:to="loc_dei_CityAreaCode_ddde9449-31a2-423f-a138-bf481818c557" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LocalPhoneNumber_7a8e59ab-2053-401e-91c7-342ae40cc229" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_LocalPhoneNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_7347df24-5a6a-4cd9-8a6a-defe94a094ac" xlink:to="loc_dei_LocalPhoneNumber_7a8e59ab-2053-401e-91c7-342ae40cc229" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_WrittenCommunications_60caa001-2f0c-41ed-82b4-a49e3e774e78" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_WrittenCommunications"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_7347df24-5a6a-4cd9-8a6a-defe94a094ac" xlink:to="loc_dei_WrittenCommunications_60caa001-2f0c-41ed-82b4-a49e3e774e78" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_SolicitingMaterial_1609c1e3-2772-4587-bfa0-01992163c742" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_SolicitingMaterial"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_7347df24-5a6a-4cd9-8a6a-defe94a094ac" xlink:to="loc_dei_SolicitingMaterial_1609c1e3-2772-4587-bfa0-01992163c742" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_PreCommencementTenderOffer_b4dcc1af-dc1b-4975-830c-a622c9c6694b" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_PreCommencementTenderOffer"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_7347df24-5a6a-4cd9-8a6a-defe94a094ac" xlink:to="loc_dei_PreCommencementTenderOffer_b4dcc1af-dc1b-4975-830c-a622c9c6694b" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_PreCommencementIssuerTenderOffer_e45926f7-6188-482b-b66c-4227f691bc35" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_PreCommencementIssuerTenderOffer"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_7347df24-5a6a-4cd9-8a6a-defe94a094ac" xlink:to="loc_dei_PreCommencementIssuerTenderOffer_e45926f7-6188-482b-b66c-4227f691bc35" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_Security12bTitle_a30509da-aae1-47d1-bed2-453e3c6c391d" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_Security12bTitle"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_7347df24-5a6a-4cd9-8a6a-defe94a094ac" xlink:to="loc_dei_Security12bTitle_a30509da-aae1-47d1-bed2-453e3c6c391d" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_TradingSymbol_721d466d-f4eb-40b9-b4d0-61082e119f87" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_TradingSymbol"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_7347df24-5a6a-4cd9-8a6a-defe94a094ac" xlink:to="loc_dei_TradingSymbol_721d466d-f4eb-40b9-b4d0-61082e119f87" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_SecurityExchangeName_d1e17de0-e073-410c-82fd-7249d428fee3" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_SecurityExchangeName"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_7347df24-5a6a-4cd9-8a6a-defe94a094ac" xlink:to="loc_dei_SecurityExchangeName_d1e17de0-e073-410c-82fd-7249d428fee3" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityEmergingGrowthCompany_332a531d-5664-4508-b8d6-d845f6dfd218" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_EntityEmergingGrowthCompany"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_7347df24-5a6a-4cd9-8a6a-defe94a094ac" xlink:to="loc_dei_EntityEmergingGrowthCompany_332a531d-5664-4508-b8d6-d845f6dfd218" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCentralIndexKey_17bc26f4-e84f-49ab-a679-72538726cd10" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_EntityCentralIndexKey"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_7347df24-5a6a-4cd9-8a6a-defe94a094ac" xlink:to="loc_dei_EntityCentralIndexKey_17bc26f4-e84f-49ab-a679-72538726cd10" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_AmendmentFlag_13ab90e3-278f-4527-858d-5b08b798d856" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_AmendmentFlag"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_7347df24-5a6a-4cd9-8a6a-defe94a094ac" xlink:to="loc_dei_AmendmentFlag_13ab90e3-278f-4527-858d-5b08b798d856" xlink:type="arc" order="21"/>
  </link:definitionLink>
</link:linkbase>
