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Debt - Summary of Long-Term Debt (Details) - USD ($)	12 Months Ended
Debt - Summary of Long-Term Debt (Details) - USD ($)	Dec. 31, 2023	Dec. 31, 2022	Apr. 21, 2021
Debt Instrument [Line Items]
Long term debt	$ 29,352,000,000	$ 31,580,000,000
Less: unamortized debt discount, premiums and debt issuance costs	(277,000,000)	(386,000,000)
Less: current portion of long-term debt	(4,018,000,000)	(2,911,000,000)
Long-term debt, net	$ 25,057,000,000	28,283,000,000
Secured Debt \| Minimum
Debt Instrument [Line Items]
Fixed interest rate	7.31%
Secured Debt \| Maximum
Debt Instrument [Line Items]
Fixed interest rate	7.35%
Secured Debt \| Aircraft notes
Debt Instrument [Line Items]
Long term debt	$ 12,508,000,000	12,262,000,000
Secured Debt \| Aircraft notes \| Minimum
Debt Instrument [Line Items]
Fixed interest rate	2.70%
Secured Debt \| Aircraft notes \| Maximum
Debt Instrument [Line Items]
Fixed interest rate	7.35%
Secured Debt \| Aircraft notes \| SOFR \| Minimum
Debt Instrument [Line Items]
Basis spread on variable rate	0.49%
Secured Debt \| Aircraft notes \| SOFR \| Maximum
Debt Instrument [Line Items]
Basis spread on variable rate	2.25%
Secured Debt \| MileagePlus Senior Secured Notes
Debt Instrument [Line Items]
Fixed interest rate	6.50%
Long term debt	$ 2,660,000,000	3,420,000,000
Secured Debt \| MileagePlus Term Loan Facility
Debt Instrument [Line Items]
Fixed interest rate	10.77%
Long term debt	$ 2,100,000,000	$ 2,700,000,000
Secured Debt \| MileagePlus Term Loan Facility \| SOFR \| Maximum
Debt Instrument [Line Items]
Basis spread on variable rate	5.25%	5.25%
Secured Debt \| 2026 and 2029 Notes
Debt Instrument [Line Items]
Long term debt	$ 4,000,000,000	$ 4,000,000,000
Secured Debt \| 2026 and 2029 Notes \| Minimum
Debt Instrument [Line Items]
Fixed interest rate	4.38%
Secured Debt \| 2026 and 2029 Notes \| Maximum
Debt Instrument [Line Items]
Fixed interest rate	4.63%
Secured Debt \| 2021 Term Loans
Debt Instrument [Line Items]
Fixed interest rate	9.22%
Long term debt	$ 3,870,000,000	$ 4,913,000,000
Aggregate principal amount			$ 5,000,000,000
Secured Debt \| 2021 Term Loans \| SOFR \| Minimum
Debt Instrument [Line Items]
Basis spread on variable rate	3.75%	3.75%
Unsecured
Debt Instrument [Line Items]
Fixed interest rate		4.25%
Unsecured \| Notes
Debt Instrument [Line Items]
Long term debt	$ 596,000,000	$ 596,000,000
Unsecured \| Notes \| Minimum
Debt Instrument [Line Items]
Fixed interest rate	4.88%
Unsecured \| Notes \| Maximum
Debt Instrument [Line Items]
Fixed interest rate	5.00%
Unsecured \| Other unsecured debt
Debt Instrument [Line Items]
Long term debt	$ 437,000,000	508,000,000
Unsecured \| Other unsecured debt \| Minimum
Debt Instrument [Line Items]
Fixed interest rate	0.00%
Unsecured \| Other unsecured debt \| Maximum
Debt Instrument [Line Items]
Fixed interest rate	5.75%
Unsecured \| PSP Notes
Debt Instrument [Line Items]
Fixed interest rate	1.00%
Long term debt	$ 3,181,000,000	$ 3,181,000,000
Unsecured \| PSP Notes \| SOFR
Debt Instrument [Line Items]
Basis spread on variable rate	2.00%
Unsecured \| PSP1 Note
Debt Instrument [Line Items]
Term of debt	10 years
Aggregate principal amount	$ 1,500,000,000
Unsecured \| PSP2 Note
Debt Instrument [Line Items]
Term of debt	10 years
Aggregate principal amount	$ 900,000,000
Unsecured \| PSP3 Note
Debt Instrument [Line Items]
Term of debt	10 years
Aggregate principal amount	$ 800,000,000