CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Operating Revenues
Total Operating Revenues	$ 10,426	$ 9,646	$ 6,176
Operating Expenses
Wages and benefits	3,041	2,640	2,218
Payroll Support Program Grant Recognized	0	0	(914)
Variable incentive pay	200	257	151
Aircraft fuel, including hedging gains and losses	2,641	2,668	1,279
Aircraft maintenance	488	424	364
Aircraft rent	208	291	254
Landing fees and other rentals	680	581	555
Contracted services	389	329	235
Selling expenses	303	295	173
Depreciation and amortization	451	415	394
Cost of Services, Catering	241	197	139
Third-party regional carrier expense	218	182	147
Other operating expenses	729	717	507
Special Items - Impairment charges and other	392	496	(1)
Restructuring Charges	0	0	(10)
Special items—other	51	84	(10)
Total Operating Expenses	10,032	9,576	5,491
Operating Income (Loss), Total	394	70	685
Nonoperating Income (Expense) [Abstract]
Investment Income, Interest	80	53	25
Interest Expense	(121)	(108)	(128)
Interest Costs Capitalized Adjustment	27	14	11
Special Items - Net non-operating	(18)	0	0
Other - net	(39)	50	36
Nonoperating Income (Expense) Total	(71)	9	(56)
Income before income tax	323	79	629
Income Tax Expense, Before Tax Cuts and Jobs Act of 2017	88	21	151
Income tax expense	88	21	151
Net Income	$ 235	$ 58	$ 478
Basic earnings per share	$ 1.84	$ 0.46	$ 3.82
Diluted earnings per share	$ 1.83	$ 0.45	$ 3.77
Shares used for computation:
Basic	127,375	126,657	125,063
Diluted	128,708	127,899	126,775
Mileage Plan Services, Other [Member]
Operating Revenues
Revenue from Contract with Customer, Excluding Assessed Tax	$ 648	$ 590	$ 461
Cargo and Freight [Member]
Operating Revenues
Revenue from Contract with Customer, Excluding Assessed Tax	252	248	216
Passenger Revenue [Member]
Operating Revenues
Revenue from Contract with Customer, Excluding Assessed Tax	9,526	8,808	5,499
Passenger Revenue [Member] | Passenger [Member]
Operating Revenues
Revenue from Contract with Customer, Excluding Assessed Tax	9,526	8,808	5,499
Mileage Plan Revenue [Member]
Operating Revenues
Revenue from Contract with Customer, Excluding Assessed Tax	1,682	1,521	1,100
Mileage Plan Revenue [Member] | Passenger [Member]
Operating Revenues
Revenue from Contract with Customer, Excluding Assessed Tax	1,034	931	639
Mileage Plan Revenue [Member] | Mileage Plan Services, Other [Member]
Operating Revenues
Revenue from Contract with Customer, Excluding Assessed Tax	648	590	461
Cargo and Other Revenue [Member]
Operating Revenues
Revenue from Contract with Customer, Excluding Assessed Tax	252	248	216
Cargo and Other Revenue [Member] | Cargo and Freight [Member]
Operating Revenues
Revenue from Contract with Customer, Excluding Assessed Tax	$ 252	$ 248	$ 216