Commitments and Contingencies - Aircraft-Related Commitments and Financing Arrangements (Details) $ in Millions	Jun. 30, 2021 USD ($) aircraft aircraft_Engine	Dec. 31, 2020
Aircraft-Related Secured Debt
Interest Commitments
Interest commitments, remainder of fiscal year	$ 49.2
Interest commitments, 2022	71.7
Interest commitments, 2023	61.0
Interest commitments, 2024	49.8
Interest commitments, 2025	42.4
Interest commitments, 2026 and thereafter	$ 96.1
8.00% senior secured notes due 2025
Interest Commitments
Stated interest rate	8.00%
8.00% senior secured notes due 2025 \| 8.00% Senior Secured Notes Due 2025
Interest Commitments
Stated interest rate	8.00%	8.00%
Non-Aircraft-Related Secured Debt, Unsecured Debt And Convertible Debt
Interest Commitments
Interest commitments, remainder of fiscal year	$ 24.6
Interest commitments, 2022	48.5
Interest commitments, 2023	48.5
Interest commitments, 2024	48.5
Interest commitments, 2025	45.5
Interest commitments, 2026 and thereafter	19.9
Aircraft and Related Flight Equipment
Committed Expenditures
Committed expenditures, remainder of fiscal year	249.2
Committed expenditures, 2022	884.7
Committed expenditures, 2023	908.7
Committed expenditures, 2024	980.0
Committed expenditures, 2025	1,066.6
Committed expenditures, 2026 and thereafter	2,248.4
Non-aircraft Related Commitments
Committed Expenditures
Committed expenditures, remainder of fiscal year	19.0
Committed expenditures, 2022	22.8
Committed expenditures, 2023	19.5
Committed expenditures, 2024	16.4
Committed expenditures, 2025	17.0
Committed expenditures, 2026 and thereafter	$ 35.6
V2500 SelectTWO Engine \| 2021-2023
Unrecorded Unconditional Purchase Obligation [Line Items]
Number of spare aircraft engines ordered \| aircraft_Engine	1
PurePower PW1100G-JM Engine \| 2021-2023
Unrecorded Unconditional Purchase Obligation [Line Items]
Number of spare aircraft engines ordered \| aircraft_Engine	2
A320 and A321
Aircraft Rent Commitments For Future Aircraft Deliveries [Abstract]
Number of delivered aircraft with secured debt financing commitments \| aircraft	72
Airbus
Unrecorded Unconditional Purchase Obligation [Line Items]
Future aircraft to be received \| aircraft	124
Number of aircraft to be delivered, remainder of fiscal year \| aircraft	4
Number of aircraft to be delivered, 2022 \| aircraft	17
Airbus \| 2021
Committed Expenditures
Number of aircraft with secured debt financing commitments scheduled for delivery \| aircraft	2
Airbus \| 2021-2027
Committed Expenditures
Number of aircraft without secured financing commitments scheduled for delivery \| aircraft	122
Third Party Lessor \| A-320-Neo
Unrecorded Unconditional Purchase Obligation [Line Items]
Future aircraft to be received \| aircraft	5
Third Party Lessor \| A320 Family
Aircraft Rent Commitments For Future Aircraft Deliveries [Abstract]
Operating lease payments expected for aircraft to be delivered, remainder of fiscal year	$ 8.7
Operating lease payments expected for aircraft to be delivered, 2022	25.8
Operating lease payments expected for aircraft to be delivered, 2023	25.8
Operating lease payments expected for aircraft to be delivered, 2024	25.8
Operating lease payments expected for aircraft to be delivered, 2025	25.8
Operating lease payments expected for aircraft to be delivered, 2026 and thereafter	$ 198.0

Aircraft Rent Commitments For Future Aircraft Deliveries

No definition available.

Name:	save_AircraftRentCommitmentsForFutureAircraftDeliveriesAbstract
Namespace Prefix:	save_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Future Aircraft To Be Received

+ References

No definition available.

+ Details

Name:	save_FutureAircraftToBeReceived
Namespace Prefix:	save_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Lessee, Operating Lease, Liability, To Be Paid, Aircraft To Be Delivered, After Year Four

+ References

No definition available.

+ Details

Name:	save_LesseeOperatingLeaseLiabilityToBePaidAircraftToBeDeliveredAfterYearFour
Namespace Prefix:	save_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Lessee, Operating Lease, Liability, To Be Paid, Aircraft To Be Delivered, Remainder Of Fiscal Year

+ References

No definition available.

+ Details

Name:	save_LesseeOperatingLeaseLiabilityToBePaidAircraftToBeDeliveredRemainderOfFiscalYear
Namespace Prefix:	save_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Lessee, Operating Lease, Liability, To Be Paid, Aircraft To Be Delivered, Year Four

+ References

No definition available.

+ Details

Name:	save_LesseeOperatingLeaseLiabilityToBePaidAircraftToBeDeliveredYearFour
Namespace Prefix:	save_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Lessee, Operating Lease, Liability, To Be Paid, Aircraft To Be Delivered, Year One

+ References

No definition available.

+ Details

Name:	save_LesseeOperatingLeaseLiabilityToBePaidAircraftToBeDeliveredYearOne
Namespace Prefix:	save_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Lessee, Operating Lease, Liability, To Be Paid, Aircraft To Be Delivered, Year Three

+ References

No definition available.

+ Details

Name:	save_LesseeOperatingLeaseLiabilityToBePaidAircraftToBeDeliveredYearThree
Namespace Prefix:	save_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Lessee, Operating Lease, Liability, To Be Paid, Aircraft To Be Delivered, Year Two

+ References

No definition available.

+ Details

Name:	save_LesseeOperatingLeaseLiabilityToBePaidAircraftToBeDeliveredYearTwo
Namespace Prefix:	save_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Long-Term Debt, Maturities, Repayments Of Interest And Fee Commitments [Abstract]

+ References

No definition available.

+ Details

Name:	save_LongTermDebtMaturitiesRepaymentsOfInterestAndFeeCommitmentsAbstract
Namespace Prefix:	save_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Long-Term Debt, Maturities, Repayments Of Interest And Fee Commitments, To Be Paid, After Year Four

+ References

No definition available.

+ Details

Name:	save_LongTermDebtMaturitiesRepaymentsOfInterestAndFeeCommitmentsToBePaidAfterYearFour
Namespace Prefix:	save_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Long-Term Debt, Maturities, Repayments Of Interest And Fee Commitments, To Be Paid, Remainder Of Fiscal Year

+ References

No definition available.

+ Details

Name:	save_LongTermDebtMaturitiesRepaymentsOfInterestAndFeeCommitmentsToBePaidRemainderOfFiscalYear
Namespace Prefix:	save_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Long-Term Debt, Maturities, Repayments Of Interest And Fee Commitments, To Be Paid, Year Four

+ References

No definition available.

+ Details

Name:	save_LongTermDebtMaturitiesRepaymentsOfInterestAndFeeCommitmentsToBePaidYearFour
Namespace Prefix:	save_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Long-Term Debt, Maturities, Repayments Of Interest And Fee Commitments, To Be Paid, Year One

+ References

No definition available.

+ Details

Name:	save_LongTermDebtMaturitiesRepaymentsOfInterestAndFeeCommitmentsToBePaidYearOne
Namespace Prefix:	save_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Long-Term Debt, Maturities, Repayments Of Interest And Fee Commitments, To Be Paid, Year Three

+ References

No definition available.

+ Details

Name:	save_LongTermDebtMaturitiesRepaymentsOfInterestAndFeeCommitmentsToBePaidYearThree
Namespace Prefix:	save_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Long-Term Debt, Maturities, Repayments Of Interest And Fee Commitments, To Be Paid, Year Two

+ References

No definition available.

+ Details

Name:	save_LongTermDebtMaturitiesRepaymentsOfInterestAndFeeCommitmentsToBePaidYearTwo
Namespace Prefix:	save_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Number Of Aircraft To Be Delivered, Remainder Of Fiscal Year

+ References

No definition available.

+ Details

Name:	save_NumberOfAircraftToBeDeliveredRemainderOfFiscalYear
Namespace Prefix:	save_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Number Of Aircraft To Be Delivered, Year One

+ References

No definition available.

+ Details

Name:	save_NumberOfAircraftToBeDeliveredYearOne
Namespace Prefix:	save_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Number of Aircraft without Secured Financing Commitments Scheduled for Delivery

+ References

No definition available.

+ Details

Name:	save_NumberOfAircraftWithoutSecuredFinancingCommitmentsScheduledForDelivery
Namespace Prefix:	save_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Number of Spare Aircraft Engines Ordered

+ References

No definition available.

+ Details

Name:	save_NumberOfSpareAircraftEnginesOrdered
Namespace Prefix:	save_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Number of Aircraft with Secured Debt Financing Commitments Scheduled for Delivery

+ References

No definition available.

+ Details

Name:	save_NumberofAircraftwithSecuredDebtFinancingCommitmentsScheduledforDelivery
Namespace Prefix:	save_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Number of Delivered Aircraft with Secured Debt Financing Commitments

+ References

No definition available.

+ Details

Name:	save_NumberofDeliveredAircraftwithSecuredDebtFinancingCommitments
Namespace Prefix:	save_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Unrecorded Unconditional Purchase Obligation, To Be Paid, After Year Four

+ References

No definition available.

+ Details

Name:	save_UnrecordedUnconditionalPurchaseObligationToBePaidAfterYearFour
Namespace Prefix:	save_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1B
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123466505&loc=SL123495323-112611

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- References

No definition available.

+ Details

Name:	us-gaap_UnrecordedUnconditionalPurchaseObligationAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of fixed and determinable portion of unrecorded unconditional purchase obligation to be paid in next fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 440
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123406679&loc=d3e25336-109308

+ Details

Name:	us-gaap_UnrecordedUnconditionalPurchaseObligationBalanceOnFirstAnniversary
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of fixed and determinable portion of unrecorded unconditional purchase obligation to be paid in fourth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

+ References

+ Details

Name:	us-gaap_UnrecordedUnconditionalPurchaseObligationBalanceOnFourthAnniversary
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of fixed and determinable portion of unrecorded unconditional purchase obligation to be paid in second fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

+ References

+ Details

Name:	us-gaap_UnrecordedUnconditionalPurchaseObligationBalanceOnSecondAnniversary
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of fixed and determinable portion of unrecorded unconditional purchase obligation to be paid in third fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

+ References

+ Details

Name:	us-gaap_UnrecordedUnconditionalPurchaseObligationBalanceOnThirdAnniversary
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of fixed and determinable portion of unrecorded unconditional purchase obligation to be paid in remainder of current fiscal year.

+ References

No definition available.

+ Details

Name:	us-gaap_UnrecordedUnconditionalPurchaseObligationDueInRemainderOfFiscalYear
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_UnrecordedUnconditionalPurchaseObligationLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_LongtermDebtTypeAxis=save_AircraftRelatedSecuredDebtMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_SecuredDebtMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=save_EightPointZeroZeroPercentSeniorSecuredNotesDueTwoThousandTwentyFiveMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=save_NonAircraftRelatedSecuredDebtUnsecuredDebtAndConvertibleDebtMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_UnrecordedUnconditionalPurchaseObligationByCategoryOfItemPurchasedAxis=us-gaap_CapitalAdditionsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_UnrecordedUnconditionalPurchaseObligationByCategoryOfItemPurchasedAxis=save_NonaircraftRelatedCommitmentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	save_EngineTypeAxis=save_V2500SelectTWOEngineMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	save_DeliveryYearAxis=save_A20212023Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	save_EngineTypeAxis=save_PurePowerPW1100GJMEngineMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_AircraftTypeAxis=save_A320andA321Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_CounterpartyNameAxis=save_AirbusMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	save_DeliveryYearAxis=save_TwoThousandTwentyOneDeliveryYearMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	save_DeliveryYearAxis=save_A20212027DeliveryYearsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_CounterpartyNameAxis=save_ThirdPartyLessorMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_AircraftTypeAxis=srt_A320NeoMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_AircraftTypeAxis=save_A320FamilyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: