CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Operating Revenues
Revenue from Contract with Customer, Excluding Assessed Tax	$ 2,838	$ 2,658	$ 5,034	$ 4,339
Operating Expenses
Wages and benefits	754	639	1,477	1,245
Variable incentive pay	57	56	104	92
Aircraft fuel, including hedging gains and losses	573	776	1,238	1,123
Aircraft maintenance	125	104	249	239
Aircraft rent	54	73	113	146
Landing fees and other rentals	167	136	319	274
Contracted services	95	82	190	160
Selling expenses	81	78	147	136
Depreciation and amortization	113	104	217	206
Food and beverage service	60	50	114	91
Third-party regional carrier expense	54	50	106	92
Other	182	177	359	329
Special items - Impairment charges and other	186	146	199	221
Special items - labor and related			51	0
Operating Expenses	2,501	2,471	4,883	4,354
Costs and Expenses, Total	2,501	2,471	4,883	4,354
Operating Income (Loss)	337	187	151	(15)
Nonoperating Income (Expense)
Interest income	22	11	39	18
Interest expense	(28)	(26)	(56)	(53)
Interest capitalized	7	3	14	5
Special items - net non-operating	(6)	0	(6)	0
Other—net	(7)	10	(16)	24
Nonoperating Income (Expense) Total	(12)	(2)	(25)	(6)
Income (Loss) Before Income Tax	325	185	126	(21)
Income tax (benefit) expense	85	46	28	(17)
Net Income (Loss)	$ 240	$ 139	$ 98	$ (4)
Basic Earnings Per Share (usd per share)	$ 1.88	$ 1.10	$ 0.77	$ (0.03)
Diluted Earnings Per Share (usd per share)	$ 1.86	$ 1.09	$ 0.76	$ (0.03)
Shares used for computation:
Basic shares (shares)	127,440,000	126,543,000	127,470,000	126,265,000
Diluted shares (shares)	128,919,000	127,795,000	128,860,000	126,265,000
Passenger [Member]
Operating Revenues
Revenue from Contract with Customer, Excluding Assessed Tax	$ 2,598	$ 2,418	$ 4,582	$ 3,929
Mileage plan other revenue [Member]
Operating Revenues
Revenue from Contract with Customer, Excluding Assessed Tax	170	175	324	287
Cargo and Freight [Member]
Operating Revenues
Revenue from Contract with Customer, Excluding Assessed Tax	70	65	128	123
Passenger Revenue [Member]
Operating Revenues
Revenue from Contract with Customer, Excluding Assessed Tax	2,598	2,418	4,582	3,929
Passenger Revenue [Member] | Passenger [Member]
Operating Revenues
Revenue from Contract with Customer, Excluding Assessed Tax	2,598	2,418	4,582	3,929
Mileage Plan Revenue [Member]
Operating Revenues
Revenue from Contract with Customer, Excluding Assessed Tax	438	422	824	722
Mileage Plan Revenue [Member] | Mileage plan other revenue [Member]
Operating Revenues
Revenue from Contract with Customer, Excluding Assessed Tax	170	175	324	287
Cargo and Other Revenue [Member]
Operating Revenues
Revenue from Contract with Customer, Excluding Assessed Tax	70	65	128	123
Cargo and Other Revenue [Member] | Cargo and Freight [Member]
Operating Revenues
Revenue from Contract with Customer, Excluding Assessed Tax	$ 70	$ 65	$ 128	$ 123