CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Operating Revenues
Revenue from Contract with Customer, Excluding Assessed Tax	$ 2,196	$ 1,681
Operating Expenses
Wages and benefits	723	606
Variable incentive pay	47	36
Aircraft fuel, including hedging gains and losses	665	347
Aircraft maintenance	124	135
Aircraft rent	59	73
Landing fees and other rentals	152	138
Contracted services	95	78
Selling expenses	66	58
Depreciation and amortization	104	102
Food and beverage service	54	41
Third-party regional carrier expense	52	42
Other	177	152
Special items - Impairment charges and other	13	75
Special items - labor and related	51	0
Operating Expenses	2,382	1,883
Costs and Expenses, Total	2,382	1,883
Operating Income (Loss)	(186)	(202)
Nonoperating Income (Expense)
Interest income	17	7
Interest expense	(28)	(27)
Interest capitalized	7	2
Other—net	(9)	14
Nonoperating Income (Expense) Total	(13)	(4)
Income (Loss) Before Income Tax	(199)	(206)
Income tax (benefit) expense	(57)	(63)
Net Income (Loss)	$ (142)	$ (143)
Basic Earnings Per Share (usd per share)	$ (1.11)	$ (1.14)
Diluted Earnings Per Share (usd per share)	$ (1.11)	$ (1.14)
Shares used for computation:
Basic shares (shares)	127,501,000	125,984,000
Diluted shares (shares)	127,501,000	125,984,000
Passenger [Member]
Operating Revenues
Revenue from Contract with Customer, Excluding Assessed Tax	$ 1,984	$ 1,511
Mileage plan other revenue [Member]
Operating Revenues
Revenue from Contract with Customer, Excluding Assessed Tax	154	112
Cargo and Freight [Member]
Operating Revenues
Revenue from Contract with Customer, Excluding Assessed Tax	58	58
Passenger Revenue [Member]
Operating Revenues
Revenue from Contract with Customer, Excluding Assessed Tax	1,984	1,511
Passenger Revenue [Member] | Passenger [Member]
Operating Revenues
Revenue from Contract with Customer, Excluding Assessed Tax	1,984	1,511
Mileage Plan Revenue [Member]
Operating Revenues
Revenue from Contract with Customer, Excluding Assessed Tax	386	300
Mileage Plan Revenue [Member] | Mileage plan other revenue [Member]
Operating Revenues
Revenue from Contract with Customer, Excluding Assessed Tax	154	112
Cargo and Other Revenue [Member]
Operating Revenues
Revenue from Contract with Customer, Excluding Assessed Tax	58	58
Cargo and Other Revenue [Member] | Cargo and Freight [Member]
Operating Revenues
Revenue from Contract with Customer, Excluding Assessed Tax	$ 58	$ 58