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

<!--XBRL Document Created with Wdesk from Workiva-->
<!--Copyright 2022 Workiva-->
<!--r:8eaf2114-eeaf-4f9c-90af-5df2b868d472,g:c82075bf-53ec-41e2-b3e9-b0bbd1064cbb-->
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:sncy="http://www.suncountry.com/20220630" xmlns:xbrli="http://www.xbrl.org/2003/instance" xmlns:dtr-types="http://www.xbrl.org/dtr/type/2020-01-21" attributeFormDefault="unqualified" elementFormDefault="qualified" targetNamespace="http://www.suncountry.com/20220630">
  <xs:import namespace="http://fasb.org/srt/2022" schemaLocation="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd"/>
  <xs:import namespace="http://fasb.org/us-gaap/2022" schemaLocation="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd"/>
  <xs:import namespace="http://www.w3.org/1999/xlink" schemaLocation="http://www.xbrl.org/2003/xlink-2003-12-31.xsd"/>
  <xs:import namespace="http://www.xbrl.org/2003/instance" schemaLocation="http://www.xbrl.org/2003/xbrl-instance-2003-12-31.xsd"/>
  <xs:import namespace="http://www.xbrl.org/2003/linkbase" schemaLocation="http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd"/>
  <xs:import namespace="http://www.xbrl.org/dtr/type/2020-01-21" schemaLocation="https://www.xbrl.org/dtr/type/2020-01-21/types.xsd"/>
  <xs:import namespace="http://xbrl.sec.gov/country/2022" schemaLocation="https://xbrl.sec.gov/country/2022/country-2022.xsd"/>
  <xs:import namespace="http://xbrl.sec.gov/dei/2022" schemaLocation="https://xbrl.sec.gov/dei/2022/dei-2022.xsd"/>
  <xs:annotation>
    <xs:appinfo>
      <link:linkbaseRef xmlns:xlink="http://www.w3.org/1999/xlink" xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:href="sncy-20220630_lab.xml" xlink:role="http://www.xbrl.org/2003/role/labelLinkbaseRef" xlink:type="simple"/>
      <link:linkbaseRef xmlns:xlink="http://www.w3.org/1999/xlink" xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:href="sncy-20220630_pre.xml" xlink:role="http://www.xbrl.org/2003/role/presentationLinkbaseRef" xlink:type="simple"/>
      <link:linkbaseRef xmlns:xlink="http://www.w3.org/1999/xlink" xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:href="sncy-20220630_cal.xml" xlink:role="http://www.xbrl.org/2003/role/calculationLinkbaseRef" xlink:type="simple"/>
      <link:linkbaseRef xmlns:xlink="http://www.w3.org/1999/xlink" xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:href="sncy-20220630_def.xml" xlink:role="http://www.xbrl.org/2003/role/definitionLinkbaseRef" xlink:type="simple"/>
      <link:roleType id="Cover" roleURI="http://www.suncountry.com/role/Cover">
        <link:definition>0001001 - Document - Cover</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CONDENSEDCONSOLIDATEDBALANCESHEETS" roleURI="http://www.suncountry.com/role/CONDENSEDCONSOLIDATEDBALANCESHEETS">
        <link:definition>1001002 - Statement - CONDENSED CONSOLIDATED BALANCE SHEETS</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CONDENSEDCONSOLIDATEDBALANCESHEETSParenthetical" roleURI="http://www.suncountry.com/role/CONDENSEDCONSOLIDATEDBALANCESHEETSParenthetical">
        <link:definition>1002003 - Statement - CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CONDENSEDCONSOLIDATEDSTATEMENTSOFOPERATIONS" roleURI="http://www.suncountry.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFOPERATIONS">
        <link:definition>1003004 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CONDENSEDCONSOLIDATEDSTATEMENTSOFCOMPREHENSIVEINCOMELOSS" roleURI="http://www.suncountry.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFCOMPREHENSIVEINCOMELOSS">
        <link:definition>1004005 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CONDENSEDCONSOLIDATEDSTATEMENTSOFCOMPREHENSIVEINCOMELOSSParenthetical" roleURI="http://www.suncountry.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFCOMPREHENSIVEINCOMELOSSParenthetical">
        <link:definition>1405401 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (Parenthetical)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CONDENSEDCONSOLIDATEDSTATEMENTSOFCHANGESINSTOCKHOLDERSEQUITY" roleURI="http://www.suncountry.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFCHANGESINSTOCKHOLDERSEQUITY">
        <link:definition>1006006 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CONDENSEDCONSOLIDATEDSTATEMENTSOFCASHFLOWS" roleURI="http://www.suncountry.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFCASHFLOWS">
        <link:definition>1007007 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="COMPANYBACKGROUND" roleURI="http://www.suncountry.com/role/COMPANYBACKGROUND">
        <link:definition>2101101 - Disclosure - COMPANY BACKGROUND</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="COMPANYBACKGROUNDOfferingsDetails" roleURI="http://www.suncountry.com/role/COMPANYBACKGROUNDOfferingsDetails">
        <link:definition>2402402 - Disclosure - COMPANY BACKGROUND - Offerings (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="COMPANYBACKGROUNDAmazonAgreementDetails" roleURI="http://www.suncountry.com/role/COMPANYBACKGROUNDAmazonAgreementDetails">
        <link:definition>2403403 - Disclosure - COMPANY BACKGROUND - Amazon Agreement (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="BASISOFPRESENTATION" roleURI="http://www.suncountry.com/role/BASISOFPRESENTATION">
        <link:definition>2104102 - Disclosure - BASIS OF PRESENTATION</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="BASISOFPRESENTATIONPolicies" roleURI="http://www.suncountry.com/role/BASISOFPRESENTATIONPolicies">
        <link:definition>2205201 - Disclosure - BASIS OF PRESENTATION (Policies)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="BASISOFPRESENTATIONTables" roleURI="http://www.suncountry.com/role/BASISOFPRESENTATIONTables">
        <link:definition>2306301 - Disclosure - BASIS OF PRESENTATION (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="BASISOFPRESENTATIONRevisionofPreviouslyIssuedConsolidatedFinancialStatementsDetails" roleURI="http://www.suncountry.com/role/BASISOFPRESENTATIONRevisionofPreviouslyIssuedConsolidatedFinancialStatementsDetails">
        <link:definition>2407404 - Disclosure - BASIS OF PRESENTATION -Revision of Previously Issued Consolidated Financial Statements (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="BASISOFPRESENTATIONInvestmentsDetails" roleURI="http://www.suncountry.com/role/BASISOFPRESENTATIONInvestmentsDetails">
        <link:definition>2408405 - Disclosure - BASIS OF PRESENTATION - Investments (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="IMPACTOFTHECOVID19PANDEMIC" roleURI="http://www.suncountry.com/role/IMPACTOFTHECOVID19PANDEMIC">
        <link:definition>2109103 - Disclosure - IMPACT OF THE COVID-19 PANDEMIC</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="IMPACTOFTHECOVID19PANDEMICDetails" roleURI="http://www.suncountry.com/role/IMPACTOFTHECOVID19PANDEMICDetails">
        <link:definition>2410406 - Disclosure - IMPACT OF THE COVID-19 PANDEMIC (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="REVENUE" roleURI="http://www.suncountry.com/role/REVENUE">
        <link:definition>2111104 - Disclosure - REVENUE</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="REVENUETables" roleURI="http://www.suncountry.com/role/REVENUETables">
        <link:definition>2312302 - Disclosure - REVENUE (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="REVENUESignificantCategoriesofOperatingRevenuesDetails" roleURI="http://www.suncountry.com/role/REVENUESignificantCategoriesofOperatingRevenuesDetails">
        <link:definition>2413407 - Disclosure - REVENUE - Significant Categories of Operating Revenues (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="REVENUEOperatingRevenuesbyGeographicRegionDetails" roleURI="http://www.suncountry.com/role/REVENUEOperatingRevenuesbyGeographicRegionDetails">
        <link:definition>2414408 - Disclosure - REVENUE - Operating Revenues by Geographic Region (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="REVENUEContractBalancesDetails" roleURI="http://www.suncountry.com/role/REVENUEContractBalancesDetails">
        <link:definition>2415409 - Disclosure - REVENUE - Contract Balances (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="REVENUELoyaltyProgramDetails" roleURI="http://www.suncountry.com/role/REVENUELoyaltyProgramDetails">
        <link:definition>2416410 - Disclosure - REVENUE - Loyalty Program (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="EARNINGSPERSHARE" roleURI="http://www.suncountry.com/role/EARNINGSPERSHARE">
        <link:definition>2117105 - Disclosure - EARNINGS PER SHARE</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="EARNINGSPERSHARETables" roleURI="http://www.suncountry.com/role/EARNINGSPERSHARETables">
        <link:definition>2318303 - Disclosure - EARNINGS PER SHARE (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="EARNINGSPERSHAREDetails" roleURI="http://www.suncountry.com/role/EARNINGSPERSHAREDetails">
        <link:definition>2419411 - Disclosure - EARNINGS PER SHARE (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="AIRCRAFT" roleURI="http://www.suncountry.com/role/AIRCRAFT">
        <link:definition>2120106 - Disclosure - AIRCRAFT</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="AIRCRAFTTables" roleURI="http://www.suncountry.com/role/AIRCRAFTTables">
        <link:definition>2321304 - Disclosure - AIRCRAFT (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="AIRCRAFTAdditionalInformationDetails" roleURI="http://www.suncountry.com/role/AIRCRAFTAdditionalInformationDetails">
        <link:definition>2422412 - Disclosure - AIRCRAFT - Additional Information (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="AIRCRAFTAircraftFleetDetails" roleURI="http://www.suncountry.com/role/AIRCRAFTAircraftFleetDetails">
        <link:definition>2423413 - Disclosure - AIRCRAFT - Aircraft Fleet (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="AIRCRAFTDepreciationAmortizationandRentExpenseonAircraftDetails" roleURI="http://www.suncountry.com/role/AIRCRAFTDepreciationAmortizationandRentExpenseonAircraftDetails">
        <link:definition>2424414 - Disclosure - AIRCRAFT - Depreciation, Amortization, and Rent Expense on Aircraft (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="DEBT" roleURI="http://www.suncountry.com/role/DEBT">
        <link:definition>2125107 - Disclosure - DEBT</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="DEBTTables" roleURI="http://www.suncountry.com/role/DEBTTables">
        <link:definition>2326305 - Disclosure - DEBT (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="DEBTLinesofCreditDetails" roleURI="http://www.suncountry.com/role/DEBTLinesofCreditDetails">
        <link:definition>2427415 - Disclosure - DEBT - Lines of Credit (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="DEBTLongtermDebtDetails" roleURI="http://www.suncountry.com/role/DEBTLongtermDebtDetails">
        <link:definition>2428416 - Disclosure - DEBT - Long-term Debt (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="DEBTLongtermDebtScheduleDetails" roleURI="http://www.suncountry.com/role/DEBTLongtermDebtScheduleDetails">
        <link:definition>2429417 - Disclosure - DEBT - Long-term Debt Schedule (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="DEBTFutureMaturitiesoftheOutstandingDebtDetails" roleURI="http://www.suncountry.com/role/DEBTFutureMaturitiesoftheOutstandingDebtDetails">
        <link:definition>2430418 - Disclosure - DEBT - Future Maturities of the Outstanding Debt (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="DEBTFutureMaturitiesoftheOutstandingDebtDetails_1" roleURI="http://www.suncountry.com/role/DEBTFutureMaturitiesoftheOutstandingDebtDetails_1">
        <link:definition>2430418 - Disclosure - DEBT - Future Maturities of the Outstanding Debt (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="DEBTFairValueDetails" roleURI="http://www.suncountry.com/role/DEBTFairValueDetails">
        <link:definition>2431419 - Disclosure - DEBT - Fair Value (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="FUELDERIVATIVESANDRISKMANAGEMENT" roleURI="http://www.suncountry.com/role/FUELDERIVATIVESANDRISKMANAGEMENT">
        <link:definition>2132108 - Disclosure - FUEL DERIVATIVES AND RISK MANAGEMENT</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="FUELDERIVATIVESANDRISKMANAGEMENTTables" roleURI="http://www.suncountry.com/role/FUELDERIVATIVESANDRISKMANAGEMENTTables">
        <link:definition>2333306 - Disclosure - FUEL DERIVATIVES AND RISK MANAGEMENT (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="FUELDERIVATIVESANDRISKMANAGEMENTAdditionalInformationDetails" roleURI="http://www.suncountry.com/role/FUELDERIVATIVESANDRISKMANAGEMENTAdditionalInformationDetails">
        <link:definition>2434420 - Disclosure - FUEL DERIVATIVES AND RISK MANAGEMENT - Additional Information (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="FUELDERIVATIVESANDRISKMANAGEMENTChangesinDerivativeAssetsLiabilitiesDetails" roleURI="http://www.suncountry.com/role/FUELDERIVATIVESANDRISKMANAGEMENTChangesinDerivativeAssetsLiabilitiesDetails">
        <link:definition>2435421 - Disclosure - FUEL DERIVATIVES AND RISK MANAGEMENT - Changes in Derivative Assets (Liabilities) (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="FUELDERIVATIVESANDRISKMANAGEMENTFuelDerivativeGainsDetails" roleURI="http://www.suncountry.com/role/FUELDERIVATIVESANDRISKMANAGEMENTFuelDerivativeGainsDetails">
        <link:definition>2436422 - Disclosure - FUEL DERIVATIVES AND RISK MANAGEMENT - Fuel Derivative Gains (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="INVESTMENTS" roleURI="http://www.suncountry.com/role/INVESTMENTS">
        <link:definition>2137109 - Disclosure - INVESTMENTS</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="InvestmentsTables" roleURI="http://www.suncountry.com/role/InvestmentsTables">
        <link:definition>2338307 - Disclosure - Investments (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="InvestmentsDetails" roleURI="http://www.suncountry.com/role/InvestmentsDetails">
        <link:definition>2439423 - Disclosure - Investments (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="FAIRVALUEMEASUREMENTS" roleURI="http://www.suncountry.com/role/FAIRVALUEMEASUREMENTS">
        <link:definition>2140110 - Disclosure - FAIR VALUE MEASUREMENTS</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="FAIRVALUEMEASUREMENTSTables" roleURI="http://www.suncountry.com/role/FAIRVALUEMEASUREMENTSTables">
        <link:definition>2341308 - Disclosure - FAIR VALUE MEASUREMENTS (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="FAIRVALUEMEASUREMENTSDetails" roleURI="http://www.suncountry.com/role/FAIRVALUEMEASUREMENTSDetails">
        <link:definition>2442424 - Disclosure - FAIR VALUE MEASUREMENTS (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="INCOMETAXES" roleURI="http://www.suncountry.com/role/INCOMETAXES">
        <link:definition>2143111 - Disclosure - INCOME TAXES</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="INCOMETAXESDetails" roleURI="http://www.suncountry.com/role/INCOMETAXESDetails">
        <link:definition>2444425 - Disclosure - INCOME TAXES (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="SPECIALITEMSNET" roleURI="http://www.suncountry.com/role/SPECIALITEMSNET">
        <link:definition>2145112 - Disclosure - SPECIAL ITEMS, NET</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="SPECIALITEMSNETTables" roleURI="http://www.suncountry.com/role/SPECIALITEMSNETTables">
        <link:definition>2346309 - Disclosure - SPECIAL ITEMS, NET (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="SPECIALITEMSNETScheduleofSpecialItemsNetDetails" roleURI="http://www.suncountry.com/role/SPECIALITEMSNETScheduleofSpecialItemsNetDetails">
        <link:definition>2447426 - Disclosure - SPECIAL ITEMS, NET - Schedule of Special Items, Net (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="COMMITMENTSANDCONTINGENCIES" roleURI="http://www.suncountry.com/role/COMMITMENTSANDCONTINGENCIES">
        <link:definition>2148113 - Disclosure - COMMITMENTS AND CONTINGENCIES</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="COMMITMENTSANDCONTINGENCIESDetails" roleURI="http://www.suncountry.com/role/COMMITMENTSANDCONTINGENCIESDetails">
        <link:definition>2449427 - Disclosure - COMMITMENTS AND CONTINGENCIES (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="OPERATINGSEGMENTS" roleURI="http://www.suncountry.com/role/OPERATINGSEGMENTS">
        <link:definition>2150114 - Disclosure - OPERATING SEGMENTS</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="OPERATINGSEGMENTSTables" roleURI="http://www.suncountry.com/role/OPERATINGSEGMENTSTables">
        <link:definition>2351310 - Disclosure - OPERATING SEGMENTS (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="OPERATINGSEGMENTSDetails" roleURI="http://www.suncountry.com/role/OPERATINGSEGMENTSDetails">
        <link:definition>2452428 - Disclosure - OPERATING SEGMENTS (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="SUBSEQUENTEVENTS" roleURI="http://www.suncountry.com/role/SUBSEQUENTEVENTS">
        <link:definition>2153115 - Disclosure - SUBSEQUENT EVENTS</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
    </xs:appinfo>
  </xs:annotation>
  <xs:element id="sncy_PropertyPlantAndEquipmentNumberOfAircraftOutstanding" abstract="false" name="PropertyPlantAndEquipmentNumberOfAircraftOutstanding" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="xbrli:decimalItemType"/>
  <xs:element id="sncy_DebtIssuanceCostsFutureAmortizationYearThree" abstract="false" name="DebtIssuanceCostsFutureAmortizationYearThree" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncy_IncomeTaxesReceivableAgreementNonCurrentLiability" abstract="false" name="IncomeTaxesReceivableAgreementNonCurrentLiability" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncy_LeaseModificationAmountReclassifiedToFinanceLeaseRightOfUseAsset" abstract="false" name="LeaseModificationAmountReclassifiedToFinanceLeaseRightOfUseAsset" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncy_LesseeFinanceLeaseLiabilityAnnualAmountToBePaid" abstract="false" name="LesseeFinanceLeaseLiabilityAnnualAmountToBePaid" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncy_LongTermDebtGrossMaturityYearFour" abstract="false" name="LongTermDebtGrossMaturityYearFour" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncy_NumberOfAircraftBoughtOutFromExistingFinanceLease" abstract="false" name="NumberOfAircraftBoughtOutFromExistingFinanceLease" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="sncy_AmortizationOfMaintenanceReserveOverMarketLiabilities" abstract="false" name="AmortizationOfMaintenanceReserveOverMarketLiabilities" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncy_DerecognitionOfOperatingLeaseObligations" abstract="false" name="DerecognitionOfOperatingLeaseObligations" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncy_IncreaseDecreaseInLessorMaintenanceDeposits" abstract="false" name="IncreaseDecreaseInLessorMaintenanceDeposits" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncy_AircraftsOperatedForAmazonMember" abstract="true" name="AircraftsOperatedForAmazonMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="sncy_NonFuelOperatingExpenses" abstract="false" name="NonFuelOperatingExpenses" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncy_LoyaltyProgramLiabilitiesNoncurrent" abstract="false" name="LoyaltyProgramLiabilitiesNoncurrent" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncy_LongTermDebtGrossMaturityRemainderOfFiscalYear" abstract="false" name="LongTermDebtGrossMaturityRemainderOfFiscalYear" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncy_LongTermDebtGrossMaturityAfterYearFour" abstract="false" name="LongTermDebtGrossMaturityAfterYearFour" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncy_OvermarketLiabilitiesCurrent" abstract="false" name="OvermarketLiabilitiesCurrent" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncy_LoyaltyProgramLiabilitiesMember" abstract="true" name="LoyaltyProgramLiabilitiesMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="sncy_ContraAssetsOutstanding" abstract="false" name="ContraAssetsOutstanding" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncy_LeaseDepositsAppliedAgainstPurchaseOfAircraft" abstract="false" name="LeaseDepositsAppliedAgainstPurchaseOfAircraft" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncy_NumberOfAircraftsFinanced" abstract="false" name="NumberOfAircraftsFinanced" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="sncy_NumberOfAircraftOwned" abstract="false" name="NumberOfAircraftOwned" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="sncy_AppraisedValueOfAircraftPurchasedOrRefinanced" abstract="false" name="AppraisedValueOfAircraftPurchasedOrRefinanced" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncy_NumberOfAircraftsUnencumbered" abstract="false" name="NumberOfAircraftsUnencumbered" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="sncy_OtherCountriesMember" abstract="true" name="OtherCountriesMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="sncy_PriorRevolvingCreditAgreementMember" abstract="true" name="PriorRevolvingCreditAgreementMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="sncy_NumberOfAircraftsFinancedUsingProceedsFromIssuanceOfPassThroughTrustCertificates" abstract="false" name="NumberOfAircraftsFinancedUsingProceedsFromIssuanceOfPassThroughTrustCertificates" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="sncy_CreditFacilitiesMember" abstract="true" name="CreditFacilitiesMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="sncy_IncreaseDecreaseToTaxReceivableAgreementLiability" abstract="false" name="IncreaseDecreaseToTaxReceivableAgreementLiability" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncy_AircraftsUnderOperatingLeasesMember" abstract="true" name="AircraftsUnderOperatingLeasesMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="sncy_ScheduleOfPropertyPlantAndEquipmentDepreciationAmortizationAndRentExpensesTableTextBlock" abstract="false" name="ScheduleOfPropertyPlantAndEquipmentDepreciationAmortizationAndRentExpensesTableTextBlock" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:textBlockItemType"/>
  <xs:element id="sncy_TermOfAgreement" abstract="false" name="TermOfAgreement" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:durationItemType"/>
  <xs:element id="sncy_A20221EETCAgreementNotesPayableMember" abstract="true" name="A20221EETCAgreementNotesPayableMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="sncy_OverMarketLiabilities" abstract="false" name="OverMarketLiabilities" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncy_IncreaseDecreaseInAirTrafficLiabilities" abstract="false" name="IncreaseDecreaseInAirTrafficLiabilities" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncy_NumberOfWarrantsThatVestOnAchievementOfEachMilestone" abstract="false" name="NumberOfWarrantsThatVestOnAchievementOfEachMilestone" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:sharesItemType"/>
  <xs:element id="sncy_NumberOfAircraftsTransferredFromOperatingToFinanceLease" abstract="false" name="NumberOfAircraftsTransferredFromOperatingToFinanceLease" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="sncy_AircraftsUnderFinanceLeasesMember" abstract="true" name="AircraftsUnderFinanceLeasesMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="sncy_ChangeInContractWithCustomerLiabilityRollForward" abstract="true" name="ChangeInContractWithCustomerLiabilityRollForward" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
  <xs:element id="sncy_SharesSurrenderedByStockholdersValueInExchangeOfPromissoryNotes" abstract="false" name="SharesSurrenderedByStockholdersValueInExchangeOfPromissoryNotes" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncy_NumberOfPurchasedAircraftsPreviouslyUnderOperatingLeases" abstract="false" name="NumberOfPurchasedAircraftsPreviouslyUnderOperatingLeases" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="sncy_IncreaseDecreaseInOperatingLeaseRightOfUseAssets" abstract="false" name="IncreaseDecreaseInOperatingLeaseRightOfUseAssets" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncy_CumulativeWarrantsVested" abstract="false" name="CumulativeWarrantsVested" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="xbrli:sharesItemType"/>
  <xs:element id="sncy_NumberOfUsedAircraftsPurchasedOrRefinanced" abstract="false" name="NumberOfUsedAircraftsPurchasedOrRefinanced" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="sncy_DebtIssuanceCostsFutureAmortizationYearOne" abstract="false" name="DebtIssuanceCostsFutureAmortizationYearOne" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncy_CargoSegmentMember" abstract="true" name="CargoSegmentMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="sncy_SCAHorusHoldingsLLCMember" abstract="true" name="SCAHorusHoldingsLLCMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="sncy_DebtIssuanceCostsFutureAmortizationReminderOfFiscalYear" abstract="false" name="DebtIssuanceCostsFutureAmortizationReminderOfFiscalYear" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncy_ProceedsFromStartUpCostsReceived" abstract="false" name="ProceedsFromStartUpCostsReceived" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncy_CashPremiumsPaid" abstract="false" name="CashPremiumsPaid" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncy_TermOfRenewalOfAgreement" abstract="false" name="TermOfRenewalOfAgreement" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:durationItemType"/>
  <xs:element id="sncy_NumberOfAircraftOwnedAndRefinanced" abstract="false" name="NumberOfAircraftOwnedAndRefinanced" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="sncy_CaresActEmployeeRetentionCredit" abstract="false" name="CaresActEmployeeRetentionCredit" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncy_A20191EETCAgreementNotesPayableMember" abstract="true" name="A20191EETCAgreementNotesPayableMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="sncy_PRInvestmentPartnersL.pMember" abstract="true" name="PRInvestmentPartnersL.pMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="sncy_DebtIssuanceCostsFutureAmortizationYearTwo" abstract="false" name="DebtIssuanceCostsFutureAmortizationYearTwo" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncy_OvermarketLiabilitiesNoncurrent" abstract="false" name="OvermarketLiabilitiesNoncurrent" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncy_NumberOfAircraftsPurchased" abstract="false" name="NumberOfAircraftsPurchased" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:decimalItemType"/>
  <xs:element id="sncy_DebtInstrumentFinancialCovenantMinimumEBITDAR" abstract="false" name="DebtInstrumentFinancialCovenantMinimumEBITDAR" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncy_PassengerAircraftMember" abstract="true" name="PassengerAircraftMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="sncy_DebtInstrumentFinancialCovenantMinimumLiquidity" abstract="false" name="DebtInstrumentFinancialCovenantMinimumLiquidity" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncy_WarrantsVestedValue" abstract="false" name="WarrantsVestedValue" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncy_DelayedDrawTermLoanFacilityMember" abstract="true" name="DelayedDrawTermLoanFacilityMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="sncy_AmazonDeferredStartUpCostsMember" abstract="true" name="AmazonDeferredStartUpCostsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="sncy_PropertyPlantAndEquipmentNumberOfAircraftReclassified" abstract="false" name="PropertyPlantAndEquipmentNumberOfAircraftReclassified" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="sncy_IncreaseDecreaseInOperatingLeaseLiabilities" abstract="false" name="IncreaseDecreaseInOperatingLeaseLiabilities" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncy_FlightSimulatorMember" abstract="true" name="FlightSimulatorMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="sncy_LongTermDebtGrossMaturityYearOne" abstract="false" name="LongTermDebtGrossMaturityYearOne" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncy_PassengerSegmentMember" abstract="true" name="PassengerSegmentMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="sncy_CaresActLoanMember" abstract="true" name="CaresActLoanMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="sncy_CargoAircraftMember" abstract="true" name="CargoAircraftMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="sncy_CostIncurredToGetCargoAircraftsReadyForServiceNumberAmortizationPeriod" abstract="false" name="CostIncurredToGetCargoAircraftsReadyForServiceNumberAmortizationPeriod" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:durationItemType"/>
  <xs:element id="sncy_IncreaseDecreaseInAircraftLeaseDeposits" abstract="false" name="IncreaseDecreaseInAircraftLeaseDeposits" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncy_NumberOfAircraftPurchasedInCurrentFiscalPeriod" abstract="false" name="NumberOfAircraftPurchasedInCurrentFiscalPeriod" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="sncy_DerivativeNonCashGainLossOnDerivativeNet" abstract="false" name="DerivativeNonCashGainLossOnDerivativeNet" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncy_TaxReceivableAgreementPercentageOfBenefitOnCashSavingsRetainedByCompany" abstract="false" name="TaxReceivableAgreementPercentageOfBenefitOnCashSavingsRetainedByCompany" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="sncy_ScheduleOfChangeInContractWithCustomerLiabilityTableTextBlock" abstract="false" name="ScheduleOfChangeInContractWithCustomerLiabilityTableTextBlock" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:textBlockItemType"/>
  <xs:element id="sncy_WarrantVestingConditionMilestoneAchievementQualifyingPaymentsReceivable" abstract="false" name="WarrantVestingConditionMilestoneAchievementQualifyingPaymentsReceivable" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncy_IncreaseDecreaseInLoyaltyProgramLiabilities" abstract="false" name="IncreaseDecreaseInLoyaltyProgramLiabilities" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncy_IncreaseDecreaseInOverMarketMaintenanceReserveLiabilities" abstract="false" name="IncreaseDecreaseInOverMarketMaintenanceReserveLiabilities" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncy_LongTermDebtGrossMaturityYearTwo" abstract="false" name="LongTermDebtGrossMaturityYearTwo" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncy_PropertyPlantAndEquipmentAcquiredThroughFinanceLeases" abstract="false" name="PropertyPlantAndEquipmentAcquiredThroughFinanceLeases" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncy_CharterServiceMember" abstract="true" name="CharterServiceMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="sncy_FinanceLeaseAssetModifications" abstract="false" name="FinanceLeaseAssetModifications" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncy_OwnedAircraftsMember" abstract="true" name="OwnedAircraftsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="sncy_IncomeTaxesReceivableAgreementNoncurrent" abstract="false" name="IncomeTaxesReceivableAgreementNoncurrent" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncy_RotablePartsMember" abstract="true" name="RotablePartsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="sncy_CertainFundsOrAccountsManagedByInvestmentAdviserSubsidiaryOfBlackrockIncMember" abstract="true" name="CertainFundsOrAccountsManagedByInvestmentAdviserSubsidiaryOfBlackrockIncMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="sncy_PercentageOfCashSavingsInFederalAndStateIncomeTaxesThatThePreIPOStockholdersRightToReceive" abstract="false" name="PercentageOfCashSavingsInFederalAndStateIncomeTaxesThatThePreIPOStockholdersRightToReceive" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="sncy_TaxReceivableAgreementAdjustment" abstract="false" name="TaxReceivableAgreementAdjustment" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncy_StockOptionsVestingBasedOnPerformanceMember" abstract="true" name="StockOptionsVestingBasedOnPerformanceMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="sncy_PropertyPlantAndEquipmentAcquiredThroughFinanceLeasesNetOfAccumulatedDepreciation" abstract="false" name="PropertyPlantAndEquipmentAcquiredThroughFinanceLeasesNetOfAccumulatedDepreciation" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncy_ImpactOfTheCovid19PandemicDisclosureTextBlock" abstract="false" name="ImpactOfTheCovid19PandemicDisclosureTextBlock" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:textBlockItemType"/>
  <xs:element id="sncy_SaleOfStockAggregatePurchasePrice" abstract="false" name="SaleOfStockAggregatePurchasePrice" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncy_AirTrafficLiabilitiesCurrent" abstract="false" name="AirTrafficLiabilitiesCurrent" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncy_DepreciationAmortizationAndRentalExpenses" abstract="false" name="DepreciationAmortizationAndRentalExpenses" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncy_AircraftMaintenanceDepositsContraAssetsMember" abstract="true" name="AircraftMaintenanceDepositsContraAssetsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="sncy_AirTrafficLiabilitiesMember" abstract="true" name="AirTrafficLiabilitiesMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="sncy_CaresActGrantsRecognized" abstract="false" name="CaresActGrantsRecognized" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncy_WarrantsVestedFairValue" abstract="false" name="WarrantsVestedFairValue" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncy_SpecialItemsOther" abstract="false" name="SpecialItemsOther" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncy_NumberOfExtensionOptions" abstract="false" name="NumberOfExtensionOptions" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="sncy_DebtIssuanceCostsFutureAmortizationAfterYearFour" abstract="false" name="DebtIssuanceCostsFutureAmortizationAfterYearFour" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncy_SharesSurrenderedByStockholdersSharesInExchangeOfPromissoryNotes" abstract="false" name="SharesSurrenderedByStockholdersSharesInExchangeOfPromissoryNotes" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:sharesItemType"/>
  <xs:element id="sncy_ContractWithCustomerLiabilityIncreaseFromLoyaltyPointsEarned" abstract="false" name="ContractWithCustomerLiabilityIncreaseFromLoyaltyPointsEarned" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncy_LongTermDebtGrossMaturityYearThree" abstract="false" name="LongTermDebtGrossMaturityYearThree" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncy_ProceedsFromStockOptionAndWarrantExercises" abstract="false" name="ProceedsFromStockOptionAndWarrantExercises" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncy_SaleOfStockSharePriceAsAPercentageOfIPOSharePrice" abstract="false" name="SaleOfStockSharePriceAsAPercentageOfIPOSharePrice" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="sncy_LongTermDebtMaturitiesRepaymentsOfPrincipalAfterYearFour" abstract="false" name="LongTermDebtMaturitiesRepaymentsOfPrincipalAfterYearFour" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncy_PercentageOfStockOptionsExpectedToMeetPerformanceConditions" abstract="false" name="PercentageOfStockOptionsExpectedToMeetPerformanceConditions" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="sncy_DecreaseInEquityDueToIncomeTaxReceivableAgreementLiability" abstract="false" name="DecreaseInEquityDueToIncomeTaxReceivableAgreementLiability" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncy_IncomeTaxReceivableAgreementLiabilityCurrent" abstract="false" name="IncomeTaxReceivableAgreementLiabilityCurrent" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncy_DerecognitionOfOperatingLeaseRightOfUseAssetsNet" abstract="false" name="DerecognitionOfOperatingLeaseRightOfUseAssetsNet" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncy_WarrantsVestedDuringPeriod" abstract="false" name="WarrantsVestedDuringPeriod" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:sharesItemType"/>
  <xs:element id="sncy_DebtIssuanceCostsFutureAmortizationYearFour" abstract="false" name="DebtIssuanceCostsFutureAmortizationYearFour" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncy_PropertyPlantAndEquipmentNumberOfAircraftReclassifiedNetChange" abstract="false" name="PropertyPlantAndEquipmentNumberOfAircraftReclassifiedNetChange" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="sncy_CostsToFulfillContractWithAmazonMember" abstract="true" name="CostsToFulfillContractWithAmazonMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="sncy_ThresholdTermOfAgreement" abstract="false" name="ThresholdTermOfAgreement" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:durationItemType"/>
  <xs:element id="sncy_GroundHandlingExpense" abstract="false" name="GroundHandlingExpense" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncy_NumberOfAircraftAcquiredInCurrentPeriod" abstract="false" name="NumberOfAircraftAcquiredInCurrentPeriod" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="sncy_OverMarketLeaseRatesContraAssetsIncludedInOperatingLeaseRightOfUseAssetsMember" abstract="true" name="OverMarketLeaseRatesContraAssetsIncludedInOperatingLeaseRightOfUseAssetsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="sncy_LoyaltyProgramLiabilitiesCurrent" abstract="false" name="LoyaltyProgramLiabilitiesCurrent" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncy_AncillaryMember" abstract="true" name="AncillaryMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="sncy_FuelDerivativeContractsMember" abstract="true" name="FuelDerivativeContractsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="sncy_NumberOfAircraftsFinancedUsingFinanceLeaseArrangement" abstract="false" name="NumberOfAircraftsFinancedUsingFinanceLeaseArrangement" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="sncy_NumberOfAircraftFinancedByDebtIssuance" abstract="false" name="NumberOfAircraftFinancedByDebtIssuance" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="sncy_AmazonAgreementMember" abstract="true" name="AmazonAgreementMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="sncy_ScheduledServiceMember" abstract="true" name="ScheduledServiceMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="sncy_AircraftLeaseDeposits" abstract="false" name="AircraftLeaseDeposits" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncy_CaresActGrantsUnderTreasuryUnderPayrollSupportProgramExtensionMember" abstract="true" name="CaresActGrantsUnderTreasuryUnderPayrollSupportProgramExtensionMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="sncy_OverMarketMaintenanceReserveLiabilitiesReclassifiedToFinanceLeaseLiability" abstract="false" name="OverMarketMaintenanceReserveLiabilitiesReclassifiedToFinanceLeaseLiability" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
</xs:schema>
