Represents the appraised value of aircraft purchased.

No definition available.

Name:	sncy_AppraisedValueOfAircraftPurchased
Namespace Prefix:	sncy_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The term prior to the expiration date of any material loyalty program securing the loan, the debt has to repaid

+ References

No definition available.

+ Details

Name:	sncy_DebtInstrumentRepaymentPeriodPriorToExpirationDateOfLoyaltyProgram
Namespace Prefix:	sncy_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of used aircraft financed or refinanced during the period with the proceeds from debt instrument.

+ References

No definition available.

+ Details

Name:	sncy_NumberOfUsedAircraftsPurchasedOrRefinanced
Namespace Prefix:	sncy_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=119993939&loc=d3e28551-108399

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400

+ Details

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

- Definition

The cash outflow during the period from the repayment of aggregate short-term and long-term debt. Excludes payment of capital lease obligations.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3291-108585

+ Details

Name:	us-gaap_RepaymentsOfDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

Name:	us-gaap_DebtInstrumentAxis=sncy_NotesPayableUnderCompanyS20191EETCAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	us-gaap_VariableRateAxis=us-gaap_LondonInterbankOfferedRateLIBORMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

DEBT - Long-term Debt (Details) $ in Thousands			13 Months Ended
DEBT - Long-term Debt (Details) $ in Thousands	Mar. 24, 2021 USD ($)	Oct. 26, 2020 USD ($)	Dec. 31, 2020 USD ($) aircraft	Mar. 31, 2021 USD ($)	Dec. 31, 2019 USD ($)
DEBT
Appraised value of aircraft purchased			$ 292,450
Notes payable under the Company's 2019-1 EETC agreement
DEBT
Face amount			$ 248,587	$ 248,587	$ 248,587
Number of used aircrafts purchased or refinanced \| aircraft			13
U. S. Department of the Treasury CARES Act Loan
DEBT
Face amount		$ 45,000
Repayment period prior to expiration date of loyalty program		6 months
Repayment of debt	$ 46,260
U. S. Department of the Treasury CARES Act Loan \| Adjusted LIBOR Rate
DEBT
Margin (as a percent)		6.50%