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

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2024 Workiva-->
<!--r:9d538a71-6465-4dc6-b0da-50133f134e03,g:cd974536-da00-4b9e-b6e6-3c9f707422d8-->
<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-20240620.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_5c366100-5129-425d-95e7-854dd9271ae9" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntitiesTable_88738d99-f1ba-40c2-b3b3-15f4ac5767b4" 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_5c366100-5129-425d-95e7-854dd9271ae9" xlink:to="loc_dei_EntitiesTable_88738d99-f1ba-40c2-b3b3-15f4ac5767b4" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityListingsExchangeAxis_ba28190c-e5fc-42b8-a072-a3e3ff432756" 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_88738d99-f1ba-40c2-b3b3-15f4ac5767b4" xlink:to="loc_dei_EntityListingsExchangeAxis_ba28190c-e5fc-42b8-a072-a3e3ff432756" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_ExchangeDomain_ba28190c-e5fc-42b8-a072-a3e3ff432756_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_ba28190c-e5fc-42b8-a072-a3e3ff432756" xlink:to="loc_dei_ExchangeDomain_ba28190c-e5fc-42b8-a072-a3e3ff432756_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_ExchangeDomain_244e73ac-2640-4b93-bdb6-b0cca078ecb3" 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_ba28190c-e5fc-42b8-a072-a3e3ff432756" xlink:to="loc_dei_ExchangeDomain_244e73ac-2640-4b93-bdb6-b0cca078ecb3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sncy_TheNasdaqStockMarketLLCMember_742aa52d-0038-4149-9807-e1063cb16beb" xlink:href="sncy-20240620.xsd#sncy_TheNasdaqStockMarketLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_ExchangeDomain_244e73ac-2640-4b93-bdb6-b0cca078ecb3" xlink:to="loc_sncy_TheNasdaqStockMarketLLCMember_742aa52d-0038-4149-9807-e1063cb16beb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentType_7774a363-dfa9-40bf-8586-bb1feaccd988" 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_5c366100-5129-425d-95e7-854dd9271ae9" xlink:to="loc_dei_DocumentType_7774a363-dfa9-40bf-8586-bb1feaccd988" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentPeriodEndDate_511e85c7-0700-4b68-b2ff-3b1eabfdbb8d" 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_5c366100-5129-425d-95e7-854dd9271ae9" xlink:to="loc_dei_DocumentPeriodEndDate_511e85c7-0700-4b68-b2ff-3b1eabfdbb8d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityRegistrantName_39028024-0c97-4f9c-a302-dd67dc049439" 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_5c366100-5129-425d-95e7-854dd9271ae9" xlink:to="loc_dei_EntityRegistrantName_39028024-0c97-4f9c-a302-dd67dc049439" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityIncorporationStateCountryCode_2474f917-7673-4395-8d9f-ae541bc584b7" 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_5c366100-5129-425d-95e7-854dd9271ae9" xlink:to="loc_dei_EntityIncorporationStateCountryCode_2474f917-7673-4395-8d9f-ae541bc584b7" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityFileNumber_00a226c0-daed-462f-8cb6-b1f0472a024c" 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_5c366100-5129-425d-95e7-854dd9271ae9" xlink:to="loc_dei_EntityFileNumber_00a226c0-daed-462f-8cb6-b1f0472a024c" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityTaxIdentificationNumber_be04e6f5-b91c-4a5e-9414-26b6a8870df2" 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_5c366100-5129-425d-95e7-854dd9271ae9" xlink:to="loc_dei_EntityTaxIdentificationNumber_be04e6f5-b91c-4a5e-9414-26b6a8870df2" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressAddressLine1_1502e61c-6721-4c59-b12c-0a6f565cb893" 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_5c366100-5129-425d-95e7-854dd9271ae9" xlink:to="loc_dei_EntityAddressAddressLine1_1502e61c-6721-4c59-b12c-0a6f565cb893" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressStateOrProvince_9b11af84-49e4-48f5-b6b5-a9d826810d44" 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_5c366100-5129-425d-95e7-854dd9271ae9" xlink:to="loc_dei_EntityAddressStateOrProvince_9b11af84-49e4-48f5-b6b5-a9d826810d44" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressPostalZipCode_1decb974-cbf2-484f-8fa9-b400c36a7306" 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_5c366100-5129-425d-95e7-854dd9271ae9" xlink:to="loc_dei_EntityAddressPostalZipCode_1decb974-cbf2-484f-8fa9-b400c36a7306" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_CityAreaCode_117afc2c-b6a7-470b-aeae-4c388eadc375" 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_5c366100-5129-425d-95e7-854dd9271ae9" xlink:to="loc_dei_CityAreaCode_117afc2c-b6a7-470b-aeae-4c388eadc375" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LocalPhoneNumber_d358c356-a457-4f76-8f24-b169168e867a" 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_5c366100-5129-425d-95e7-854dd9271ae9" xlink:to="loc_dei_LocalPhoneNumber_d358c356-a457-4f76-8f24-b169168e867a" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_WrittenCommunications_80134ca5-8f1c-460f-b099-e27fe8756bac" 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_5c366100-5129-425d-95e7-854dd9271ae9" xlink:to="loc_dei_WrittenCommunications_80134ca5-8f1c-460f-b099-e27fe8756bac" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_SolicitingMaterial_603eb443-172a-4c85-a64d-88d8fc60912d" 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_5c366100-5129-425d-95e7-854dd9271ae9" xlink:to="loc_dei_SolicitingMaterial_603eb443-172a-4c85-a64d-88d8fc60912d" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_PreCommencementTenderOffer_dacfb38c-ff79-43c5-97e7-7cbc92d62cdc" 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_5c366100-5129-425d-95e7-854dd9271ae9" xlink:to="loc_dei_PreCommencementTenderOffer_dacfb38c-ff79-43c5-97e7-7cbc92d62cdc" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_PreCommencementIssuerTenderOffer_75530196-cdd2-4522-9d1f-98e401499b79" 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_5c366100-5129-425d-95e7-854dd9271ae9" xlink:to="loc_dei_PreCommencementIssuerTenderOffer_75530196-cdd2-4522-9d1f-98e401499b79" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_Security12bTitle_b40329e3-4106-480d-bb4b-5a79482c121d" 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_5c366100-5129-425d-95e7-854dd9271ae9" xlink:to="loc_dei_Security12bTitle_b40329e3-4106-480d-bb4b-5a79482c121d" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_TradingSymbol_2a856051-48da-4e5c-aca9-e0f46b275f4a" 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_5c366100-5129-425d-95e7-854dd9271ae9" xlink:to="loc_dei_TradingSymbol_2a856051-48da-4e5c-aca9-e0f46b275f4a" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityEmergingGrowthCompany_36a82704-97ee-4079-a3e9-7c82361ed7ed" 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_5c366100-5129-425d-95e7-854dd9271ae9" xlink:to="loc_dei_EntityEmergingGrowthCompany_36a82704-97ee-4079-a3e9-7c82361ed7ed" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityExTransitionPeriod_d6f3cc24-fb3f-4c88-b652-52b007404588" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityExTransitionPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_5c366100-5129-425d-95e7-854dd9271ae9" xlink:to="loc_dei_EntityExTransitionPeriod_d6f3cc24-fb3f-4c88-b652-52b007404588" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCentralIndexKey_f2f332d9-3205-45c2-a7aa-3ba49c4650af" 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_5c366100-5129-425d-95e7-854dd9271ae9" xlink:to="loc_dei_EntityCentralIndexKey_f2f332d9-3205-45c2-a7aa-3ba49c4650af" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_AmendmentFlag_bb826b7d-e071-4251-8bb3-16d1669fb906" 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_5c366100-5129-425d-95e7-854dd9271ae9" xlink:to="loc_dei_AmendmentFlag_bb826b7d-e071-4251-8bb3-16d1669fb906" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_SecurityExchangeName_e8c78aa8-27e0-4c51-a8c8-31d5389820e5" 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_5c366100-5129-425d-95e7-854dd9271ae9" xlink:to="loc_dei_SecurityExchangeName_e8c78aa8-27e0-4c51-a8c8-31d5389820e5" xlink:type="arc" order="21"/>
  </link:definitionLink>
</link:linkbase>
