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

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2025 Workiva-->
<!--r:f0af6f52-8ff1-4329-83a2-91d2165832c8,g:5e4a1511-b555-494c-9b3d-066ebe75039a-->
<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-20250204.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_c1983b0a-28d9-4944-b0f5-d79a6683ffaa" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntitiesTable_27f77406-ee10-4f00-8a69-fa48fb61274e" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntitiesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_dei_EntityInformationLineItems_c1983b0a-28d9-4944-b0f5-d79a6683ffaa" xlink:to="loc_dei_EntitiesTable_27f77406-ee10-4f00-8a69-fa48fb61274e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityListingsExchangeAxis_69c7be67-2aaf-464f-b219-30a8c2085d4a" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityListingsExchangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_dei_EntitiesTable_27f77406-ee10-4f00-8a69-fa48fb61274e" xlink:to="loc_dei_EntityListingsExchangeAxis_69c7be67-2aaf-464f-b219-30a8c2085d4a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_ExchangeDomain_69c7be67-2aaf-464f-b219-30a8c2085d4a_default" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_ExchangeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_EntityListingsExchangeAxis_69c7be67-2aaf-464f-b219-30a8c2085d4a" xlink:to="loc_dei_ExchangeDomain_69c7be67-2aaf-464f-b219-30a8c2085d4a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_ExchangeDomain_cbe83554-b668-4b59-8082-5e9bdee35a73" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_ExchangeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_EntityListingsExchangeAxis_69c7be67-2aaf-464f-b219-30a8c2085d4a" xlink:to="loc_dei_ExchangeDomain_cbe83554-b668-4b59-8082-5e9bdee35a73" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_TheNasdaqStockMarketLLCMember_1d871704-94ae-4620-8f52-88f110176b02" xlink:href="sncy-20250204.xsd#sncy_TheNasdaqStockMarketLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_ExchangeDomain_cbe83554-b668-4b59-8082-5e9bdee35a73" xlink:to="loc_sncy_TheNasdaqStockMarketLLCMember_1d871704-94ae-4620-8f52-88f110176b02" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentType_8a413098-2016-4f80-849b-80626a56daee" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_DocumentType"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_c1983b0a-28d9-4944-b0f5-d79a6683ffaa" xlink:to="loc_dei_DocumentType_8a413098-2016-4f80-849b-80626a56daee" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentPeriodEndDate_1ead0e29-c555-47d5-9537-6dd62146e6aa" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_DocumentPeriodEndDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_c1983b0a-28d9-4944-b0f5-d79a6683ffaa" xlink:to="loc_dei_DocumentPeriodEndDate_1ead0e29-c555-47d5-9537-6dd62146e6aa" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityRegistrantName_e1e24c53-4603-417f-88eb-af853c87aa45" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityRegistrantName"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_c1983b0a-28d9-4944-b0f5-d79a6683ffaa" xlink:to="loc_dei_EntityRegistrantName_e1e24c53-4603-417f-88eb-af853c87aa45" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityIncorporationStateCountryCode_9a6725c0-a7ef-450b-a44d-ac195d5f0c70" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityIncorporationStateCountryCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_c1983b0a-28d9-4944-b0f5-d79a6683ffaa" xlink:to="loc_dei_EntityIncorporationStateCountryCode_9a6725c0-a7ef-450b-a44d-ac195d5f0c70" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityFileNumber_e0295328-772d-4dee-804b-f3f65e65b143" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityFileNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_c1983b0a-28d9-4944-b0f5-d79a6683ffaa" xlink:to="loc_dei_EntityFileNumber_e0295328-772d-4dee-804b-f3f65e65b143" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityTaxIdentificationNumber_1c14e414-9e37-4ad0-a26a-e7d5b12837e2" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityTaxIdentificationNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_c1983b0a-28d9-4944-b0f5-d79a6683ffaa" xlink:to="loc_dei_EntityTaxIdentificationNumber_1c14e414-9e37-4ad0-a26a-e7d5b12837e2" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressAddressLine1_5dbc37b4-241e-4613-b207-840874a1bfee" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityAddressAddressLine1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_c1983b0a-28d9-4944-b0f5-d79a6683ffaa" xlink:to="loc_dei_EntityAddressAddressLine1_5dbc37b4-241e-4613-b207-840874a1bfee" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressCityOrTown_c97d5eb8-45f7-4fd0-ac2e-9742d55d1305" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityAddressCityOrTown"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_c1983b0a-28d9-4944-b0f5-d79a6683ffaa" xlink:to="loc_dei_EntityAddressCityOrTown_c97d5eb8-45f7-4fd0-ac2e-9742d55d1305" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressStateOrProvince_ece6b918-6fd3-4ac8-a9d0-d3ee31eae934" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityAddressStateOrProvince"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_c1983b0a-28d9-4944-b0f5-d79a6683ffaa" xlink:to="loc_dei_EntityAddressStateOrProvince_ece6b918-6fd3-4ac8-a9d0-d3ee31eae934" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressPostalZipCode_02f452b9-dfa5-457f-a56b-2adad6e98435" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityAddressPostalZipCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_c1983b0a-28d9-4944-b0f5-d79a6683ffaa" xlink:to="loc_dei_EntityAddressPostalZipCode_02f452b9-dfa5-457f-a56b-2adad6e98435" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_CityAreaCode_7c5ee44a-eb0d-4b88-a49b-33b9a1d522b6" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_CityAreaCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_c1983b0a-28d9-4944-b0f5-d79a6683ffaa" xlink:to="loc_dei_CityAreaCode_7c5ee44a-eb0d-4b88-a49b-33b9a1d522b6" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LocalPhoneNumber_fffb8c81-8c62-469c-bc9a-0d1d1d412456" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_LocalPhoneNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_c1983b0a-28d9-4944-b0f5-d79a6683ffaa" xlink:to="loc_dei_LocalPhoneNumber_fffb8c81-8c62-469c-bc9a-0d1d1d412456" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_WrittenCommunications_9d735a19-e39d-4712-9e44-d6a786e84a5b" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_WrittenCommunications"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_c1983b0a-28d9-4944-b0f5-d79a6683ffaa" xlink:to="loc_dei_WrittenCommunications_9d735a19-e39d-4712-9e44-d6a786e84a5b" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_SolicitingMaterial_171e41c5-dd77-4714-9ce6-95673453330f" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_SolicitingMaterial"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_c1983b0a-28d9-4944-b0f5-d79a6683ffaa" xlink:to="loc_dei_SolicitingMaterial_171e41c5-dd77-4714-9ce6-95673453330f" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_PreCommencementTenderOffer_8e1cd2f6-15b1-4667-9b50-f110304b8dc1" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_PreCommencementTenderOffer"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_c1983b0a-28d9-4944-b0f5-d79a6683ffaa" xlink:to="loc_dei_PreCommencementTenderOffer_8e1cd2f6-15b1-4667-9b50-f110304b8dc1" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_PreCommencementIssuerTenderOffer_7dd59fd7-76a2-4f95-b070-87490284593c" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_PreCommencementIssuerTenderOffer"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_c1983b0a-28d9-4944-b0f5-d79a6683ffaa" xlink:to="loc_dei_PreCommencementIssuerTenderOffer_7dd59fd7-76a2-4f95-b070-87490284593c" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_Security12bTitle_8a9b7820-4bb7-4fed-be6b-5e9d20aca561" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_Security12bTitle"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_c1983b0a-28d9-4944-b0f5-d79a6683ffaa" xlink:to="loc_dei_Security12bTitle_8a9b7820-4bb7-4fed-be6b-5e9d20aca561" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_TradingSymbol_5305113e-a2a6-49c1-af87-9ea3d0fd9c33" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_TradingSymbol"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_c1983b0a-28d9-4944-b0f5-d79a6683ffaa" xlink:to="loc_dei_TradingSymbol_5305113e-a2a6-49c1-af87-9ea3d0fd9c33" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_SecurityExchangeName_75dbae30-b858-487f-ab91-5295eaabc0ad" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_SecurityExchangeName"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_c1983b0a-28d9-4944-b0f5-d79a6683ffaa" xlink:to="loc_dei_SecurityExchangeName_75dbae30-b858-487f-ab91-5295eaabc0ad" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityEmergingGrowthCompany_6a59fd03-12e5-49f3-bdea-c1665da45114" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityEmergingGrowthCompany"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_c1983b0a-28d9-4944-b0f5-d79a6683ffaa" xlink:to="loc_dei_EntityEmergingGrowthCompany_6a59fd03-12e5-49f3-bdea-c1665da45114" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCentralIndexKey_2b4cdf3b-a0fb-4d74-8344-57c3b4535eaf" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityCentralIndexKey"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_c1983b0a-28d9-4944-b0f5-d79a6683ffaa" xlink:to="loc_dei_EntityCentralIndexKey_2b4cdf3b-a0fb-4d74-8344-57c3b4535eaf" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_AmendmentFlag_5ba05438-ff64-434e-b750-af6d96c909d5" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_AmendmentFlag"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_c1983b0a-28d9-4944-b0f5-d79a6683ffaa" xlink:to="loc_dei_AmendmentFlag_5ba05438-ff64-434e-b750-af6d96c909d5" xlink:type="arc" order="21"/>
  </link:definitionLink>
</link:linkbase>
