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Significant Accounting Policies - Narrative (Details) $ in Millions | 12 Months Ended
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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

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