Income Taxes (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
DEFERRED TAX LIABILITIES:
Accelerated depreciation	$ 3,279	$ 2,883
Prepaid insurance	238	189
Operating lease liabilities	311	356
Other	154	188
Total deferred tax liabilities	3,982	3,616
DEFERRED TAX ASSETS:
Accrued employee benefits	424	341
Rapid rewards loyalty liability	616	636
Operating lease liabilities	313	371
Customer flight credits	43	305
Net operating losses and tax credits (a)	310	36
Other	291	157
Total deferred tax assets	1,997	1,846
Net deferred tax liability	1,985	1,770
CURRENT:
Federal	(36)	337	$ (273)
State	(3)	33	(5)
Change in federal statutory rate	0	(2)	(188)
Total current	(39)	368	(466)
DEFERRED:
Federal	208	(43)	(589)
State	20	23	(127)
Total deferred	228	(20)	(716)
Total income tax provision (benefit)	189	348	(1,182)
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Taxes receivable	133	699
Income Tax Expense (Benefit), Continuing Operations, Income Tax Reconciliation [Abstract]
Tax at statutory U.S. tax rates	153	278	(894)
State income taxes, net of federal benefit	12	45	(115)
Change in federal statutory tax rate	0	(2)	(188)
Effective Income Tax Rate Reconciliation, Convertible Debt Repurchases, Amount	31	21	10
Effective Income Tax Rate Reconciliation, Tax Credit, Amount	(13)	(2)	(1)
Other, net	6	8	6
Total income tax provision (benefit)	189	348	$ (1,182)
State and Local Jurisdiction
DEFERRED TAX ASSETS:
Operating loss carryforwards	43	44
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Operating loss carryforwards	43	44
Domestic Tax Authority
DEFERRED TAX ASSETS:
Operating loss carryforwards	275
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Operating loss carryforwards	275
CARES Act
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Taxes receivable	$ 472	$ 472