CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Operating Revenues
Total Operating Revenues	$ 701.0	$ 2,389.0	$ 2,758.0	$ 6,553.0
Costs and Expenses, Total	1,272.0	1,967.0	3,938.0	5,742.0
Wages and benefits	495.0	608.0	1,579.0	1,732.0
Variable incentive pay	42.0	46.0	65.0	125.0
Aircraft fuel, including hedging gains and losses	125.0	486.0	568.0	1,408.0
Aircraft maintenance	84.0	106.0	244.0	341.0
Aircraft rent	74.0	82.0	229.0	247.0
Landing fees and other rentals	109.0	143.0	323.0	388.0
Contracted services	36.0	72.0	138.0	214.0
Selling expenses	24.0	77.0	83.0	236.0
Depreciation and amortization	105.0	106.0	320.0	317.0
Food and beverage service	14.0	57.0	70.0	159.0
Third-party regional carrier expense	29.0	42.0	92.0	125.0
Other	89.0	137.0	310.0	411.0
Special items - merger-related costs	1.0	5.0	5.0	39.0
Operating Income (Loss)	(571.0)	422.0	(1,180.0)	811.0
Nonoperating Income (Expense)
Interest income	7.0	11.0	23.0	31.0
Interest Costs Incurred	34.0	18.0	64.0	60.0
Interest capitalized	4.0	4.0	8.0	11.0
Other—net	5.0	(3.0)	16.0	(20.0)
Nonoperating Income (Expense) Total	(18.0)	(6.0)	(17.0)	(38.0)
Income (Loss) Before Income Tax	(589.0)	416.0	(1,197.0)	773.0
Income tax (benefit) expense	(158.0)	94.0	(320.0)	185.0
Net Income (Loss)	$ (431.0)	$ 322.0	$ (877.0)	$ 588.0
Basic Earnings Per Share (usd per share)	$ (3.49)	$ 2.61	$ (7.12)	$ 4.76
Diluted Earnings Per Share (usd per share)	$ (3.49)	$ 2.60	$ (7.12)	$ 4.74
Shares used for computation:
Basic shares (shares)	123,647	123,280	123,255	123,330
Diluted shares (shares)	123,647	124,067	123,255	124,051
Special items - Impairment charges and other	$ 121.0	$ 0.0	$ 350.0	$ 0.0
Restructuring Charges	322.0	0.0	322.0	0.0
Increase (Decrease) in Contract with Customer, Liability			171.0	244.0
PSPGrantRecognized	(398.0)	0.0	(760.0)	0.0
ProceedsFromPayrollSupportProgramGrant			753.0	0.0
Passenger Revenue [Member]
Operating Revenues
Revenue from Contract with Customer, Excluding Assessed Tax	572.0	2,211.0	2,362.0	6,038.0
Passenger Revenue [Member] | Passenger [Member]
Operating Revenues
Revenue from Contract with Customer, Excluding Assessed Tax	572.0	2,211.0	2,362.0	6,038.0
Mileage Plan Revenue [Member]
Operating Revenues
Revenue from Contract with Customer, Excluding Assessed Tax	148.0	304.0	538.0	857.0
Mileage Plan Revenue [Member] | Passenger [Member]
Operating Revenues
Revenue from Contract with Customer, Excluding Assessed Tax	64.0	186.0	272.0	511.0
Mileage Plan Revenue [Member] | Mileage plan other revenue [Member]
Operating Revenues
Revenue from Contract with Customer, Excluding Assessed Tax	84.0	118.0	266.0	346.0
Cargo and Other Revenue [Member]
Operating Revenues
Revenue from Contract with Customer, Excluding Assessed Tax	45.0	60.0	130.0	169.0
Cargo and Other Revenue [Member] | Cargo and Freight [Member]
Operating Revenues
Revenue from Contract with Customer, Excluding Assessed Tax	$ 45.0	$ 60.0	$ 130.0	$ 169.0