CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Operating Revenues
Total Operating Revenues	$ 797	$ 1,636
Operating Expenses
Wages and benefits	493	612
Variable incentive pay	33	7
PSPGrantRecognized	(411)	0
Aircraft fuel, including hedging gains and losses	203	384
Aircraft maintenance	81	115
Aircraft rent	62	81
Landing fees and other rentals	129	131
Contracted services	51	72
Selling expenses	33	55
Depreciation and amortization	97	108
Food and beverage service	23	49
Third-party regional carrier expense	30	37
Other	105	143
Special items - Impairment charges and other	18	160
Restructuring Charges	11	0
Special items - merger-related costs	0	3
Costs and Expenses, Total	958	1,957
Operating Income (Loss)	(161)	(321)
Nonoperating Income (Expense)
Interest income	7	9
Interest Costs Incurred	(32)	(13)
Interest capitalized	3	3
Other—net	10	5
Nonoperating Income (Expense) Total	(12)	4
Income (Loss) Before Income Tax	(173)	(317)
Income tax (benefit) expense	(42)	(85)
Net Income (Loss)	$ (131)	$ (232)
Basic Earnings Per Share (usd per share)	$ (1.05)	$ (1.89)
Diluted Earnings Per Share (usd per share)	$ (1.05)	$ (1.89)
Shares used for computation:
Basic shares (shares)	124,299,000	122,818,000
Diluted shares (shares)	124,299,000	122,818,000
Passenger Revenue [Member]
Operating Revenues
Revenue from Contract with Customer, Excluding Assessed Tax	$ 659	$ 1,481
Passenger Revenue [Member] | Passenger [Member]
Operating Revenues
Revenue from Contract with Customer, Excluding Assessed Tax	659	1,481
Mileage Plan Revenue [Member]
Operating Revenues
Revenue from Contract with Customer, Excluding Assessed Tax	178	261
Mileage Plan Revenue [Member] | Mileage plan other revenue [Member]
Operating Revenues
Revenue from Contract with Customer, Excluding Assessed Tax	94	109
Cargo and Other Revenue [Member]
Operating Revenues
Revenue from Contract with Customer, Excluding Assessed Tax	44	46
Cargo and Other Revenue [Member] | Cargo and Freight [Member]
Operating Revenues
Revenue from Contract with Customer, Excluding Assessed Tax	$ 44	$ 46