CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Operating Revenues
Revenue from Contract with Customer, Excluding Assessed Tax	$ 3,072	$ 2,839	$ 8,201	$ 7,873
Operating Expenses
Wages and benefits	883	782	2,469	2,259
Variable incentive pay	104	45	197	149
Aircraft fuel, including hedging gains and losses	624	694	1,804	1,932
Aircraft maintenance	140	118	391	367
Aircraft rent	49	48	142	161
Landing fees and other rentals	194	183	532	502
Contracted services	108	100	311	290
Selling expenses	82	84	243	231
Depreciation and amortization	139	113	393	330
Food and beverage service	69	62	194	176
Third-party regional carrier expense	63	58	181	164
Other	202	185	593	544
Special items - Impairment charges and other	74	156	254	406
Costs and Expenses, Total	2,731	2,628	7,704	7,511
Operating Income (Loss)	341	211	497	362
Nonoperating Income (Expense)
Interest income	28	23	69	62
Interest expense	(44)	(34)	(115)	(90)
Interest capitalized	7	7	19	21
Special items - net non-operating	(1)	(8)	(1)	(14)
Other—net	(3)	(6)	(3)	(22)
Nonoperating Income (Expense) Total	(13)	(18)	(31)	(43)
Income (Loss) Before Income Tax	328	193	466	319
Income tax (benefit) expense	92	54	142	82
Net Income (Loss)	$ 236	$ 139	$ 324	$ 237
Basic Earnings Per Share (usd per share)	$ 1.87	$ 1.09	$ 2.57	$ 1.86
Diluted Earnings Per Share (usd per share)	$ 1.84	$ 1.08	$ 2.52	$ 1.84
Shares used for computation:
Basic shares (shares)	126,189,000	127,187,000	126,165,000	127,375,000
Diluted shares (shares)	128,590,000	129,188,000	128,347,000	129,085,000.000
Passenger [Member]
Operating Revenues
Revenue from Contract with Customer, Excluding Assessed Tax	$ 2,821	$ 2,618	$ 7,476	$ 7,200
Mileage plan other revenue [Member]
Operating Revenues
Revenue from Contract with Customer, Excluding Assessed Tax	171	159	509	483
Cargo and Freight [Member]
Operating Revenues
Revenue from Contract with Customer, Excluding Assessed Tax	80	62	216	190
Passenger Revenue [Member]
Operating Revenues
Revenue from Contract with Customer, Excluding Assessed Tax	2,821	2,618	7,476	7,200
Passenger Revenue [Member] | Passenger [Member]
Operating Revenues
Revenue from Contract with Customer, Excluding Assessed Tax	2,821	2,618	7,476	7,200
Mileage Plan Revenue [Member]
Operating Revenues
Revenue from Contract with Customer, Excluding Assessed Tax	460	416	1,336	1,240
Mileage Plan Revenue [Member] | Mileage plan other revenue [Member]
Operating Revenues
Revenue from Contract with Customer, Excluding Assessed Tax	171	159	509	483
Cargo and Other Revenue [Member]
Operating Revenues
Revenue from Contract with Customer, Excluding Assessed Tax	80	62	216	190
Cargo and Other Revenue [Member] | Cargo and Freight [Member]
Operating Revenues
Revenue from Contract with Customer, Excluding Assessed Tax	$ 80	$ 62	$ 216	$ 190