Percentage of stock options expected to meet performance conditions and are hence, included in dilutive options.

No definition available.

Name:	sncy_PercentageOfStockOptionsExpectedToMeetPerformanceConditions
Namespace Prefix:	sncy_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

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

- Definition

Exercise price per share or per unit of warrants or rights outstanding.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21475-112644

+ Details

Name:	us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

Additional shares included in the calculation of diluted EPS as a result of the potentially dilutive effect of call options and warrants using the treasury stock method.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 26
-URI http://asc.fasb.org/extlink&oid=121326447&loc=d3e1828-109256

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 23
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=121326447&loc=d3e1757-109256

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 22
-URI http://asc.fasb.org/extlink&oid=121326447&loc=d3e1707-109256

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257

+ Details

Name:	us-gaap_IncrementalCommonSharesAttributableToCallOptionsAndWarrants
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of non-vested options outstanding.

+ References

No definition available.

+ Details

Name:	us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedNumberOfShares
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Details

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

- Details

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

- Details

Name:	us-gaap_AwardTypeAxis=sncy_StockOptionsVestingBasedOnPerformanceMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

EARNINGS PER SHARE (Details) - $ / shares		3 Months Ended
EARNINGS PER SHARE (Details) - $ / shares	Jan. 30, 2020	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020	Jan. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Apr. 11, 2018
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Outstanding shares						40,005,885
Warrents held	40,005,885
Exercise price (in dollars per share)	$ 0.0005					$ 0.0005
Apollo
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Outstanding shares					40,005,885
Exercise price (in dollars per share)								$ 0.0005
Amazon
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Exercise price (in dollars per share)			$ 15.17
Performance-based stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Outstanding shares		3,557,432	3,577,252	3,646,690		3,502,925	3,583,923
Percentage Of Stock Options Expected To Meet Performance Conditions		75.00%