Significant Accounting Policies - Narrative (Details) $ in Millions	12 Months Ended
	Dec. 31, 2023 USD ($) segment	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Summary Of Significant Accounting Policies [Line Items]
Expiration period for refundable tickets	1 year
Expiration period for advance ticket sales	12 months
Number of operating segments | segment	1
Revenue	$ 53,717	$ 44,955	$ 24,634
Period over which miles are expected to be redeemed	two years
Senior secured notes	$ 4,800
Carrying value of computer software	453	471
Impairment, long-lived asset			$ 97
Impairment, Long-Lived Asset, Held-for-Use, Statement of Income or Comprehensive Income [Extensible Enumeration]			Restructuring, Settlement and Impairment Provisions
Amortization expense	37	41	$ 49
Projected amortization expense in 2024	32
Projected amortization expense in 2025	28
Projected amortization expense in 2026	18
Projected amortization expense in 2027	11
Projected amortization expense in 2028	10
Advertising expense	$ 221	165	99
Minimum
Summary Of Significant Accounting Policies [Line Items]
Term for frequent flyer mileage sales to partners	1 year
Maximum
Summary Of Significant Accounting Policies [Line Items]
Term for frequent flyer mileage sales to partners	6 years
Computer software
Summary Of Significant Accounting Policies [Line Items]
Depreciation expense	$ 168	166	182
Advance Ticket Sales
Summary Of Significant Accounting Policies [Line Items]
Revenue recognized	5,700	3,300	1,800
Ancillary Fees Recorded within Passenger Revenues
Summary Of Significant Accounting Policies [Line Items]
Revenue	4,100	3,400	2,200
Other Operating Revenue
Summary Of Significant Accounting Policies [Line Items]
Revenue	3,176	2,752	2,088
Other Operating Revenue | Chase and Other Partner Agreements
Summary Of Significant Accounting Policies [Line Items]
Revenue	$ 2,700	$ 2,400	$ 1,800