CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating Revenues
Total Operating Revenues		$ 8,781	$ 8,264	$ 7,894
Operating Expenses
Wages and benefits		2,370	2,190	1,931
Variable incentive pay		163	147	135
Aircraft fuel, including hedging gains and losses		1,878	1,936	1,447
Aircraft maintenance		437	435	391
Aircraft rent		331	315	274
Landing fees and other rentals		531	499	460
Contracted services		289	306	314
Selling expense		313	326	368
Depreciation and amortization		423	398	372
Cost of Services, Catering		214	211	195
Third-party regional carrier expense		166	154	121
Other operating expenses		559	572	562
Special items - merger-related costs		44	87	116
Special items—other		0	45	0
Total Operating Expenses		7,718	7,621	6,686
Operating Income		1,063	643	1,208
Non-operating Income (Expense)
Interest income		42	38	34
Interest expense		(78)	(91)	(103)
Interest capitalized		15	18	17
Other - net		(26)	(23)	3
Nonoperating Income (Expense) Total		(47)	(58)	(49)
Income before income tax		1,016	585	1,159
Income Tax Expense, Before Tax Cuts and Jobs Act of 2017		247	148	436
Special tax expense (benefit)		0	0	(237)
Income tax expense		247	148	199
Net Income		$ 769	$ 437	$ 960
Basic earnings per share		$ 6.24	$ 3.55	$ 7.79
Diluted earnings per share		$ 6.19	$ 3.52	$ 7.75
Shares used for computation:
Basic		123,279	123,230	123,211
Diluted		124,289	123,975	123,854
Cash dividend declared per share	$ 0.35	$ 1.40
Mileage Plan Services, Other [Member]
Operating Revenues
Revenue from Contract with Customer, Excluding Assessed Tax		$ 465	$ 434	$ 418
Cargo and Freight [Member]
Operating Revenues
Revenue from Contract with Customer, Excluding Assessed Tax		221	199	175
Passenger Revenue [Member]
Operating Revenues
Revenue from Contract with Customer, Excluding Assessed Tax		8,095	7,631	7,301
Passenger Revenue [Member] | Passenger [Member]
Operating Revenues
Revenue from Contract with Customer, Excluding Assessed Tax		8,095	7,631	7,301
Mileage Plan Revenue [Member]
Operating Revenues
Revenue from Contract with Customer, Excluding Assessed Tax		1,169	1,053	959
Mileage Plan Revenue [Member] | Passenger [Member]
Operating Revenues
Revenue from Contract with Customer, Excluding Assessed Tax		704	619	541
Mileage Plan Revenue [Member] | Mileage Plan Services, Other [Member]
Operating Revenues
Revenue from Contract with Customer, Excluding Assessed Tax		465	434	418
Cargo and Other Revenue [Member]
Operating Revenues
Revenue from Contract with Customer, Excluding Assessed Tax		221	199	175
Cargo and Other Revenue [Member] | Cargo and Freight [Member]
Operating Revenues
Revenue from Contract with Customer, Excluding Assessed Tax		$ 221	$ 199	$ 175