CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Operating Revenues
Total Operating Revenues	$ 2,389	$ 2,212	$ 6,553	$ 6,200
Operating Expenses
Wages and benefits	608	549	1,732	1,629
Variable incentive pay	46	27	125	104
Aircraft fuel, including hedging gains and losses	486	513	1,408	1,397
Aircraft maintenance	106	107	341	320
Aircraft rent	82	82	247	233
Landing fees and other rentals	143	135	388	371
Contracted services	72	70	214	227
Selling expenses	77	79	236	245
Depreciation and amortization	106	99	317	290
Food and beverage service	57	53	159	158
Third-party regional carrier expense	42	38	125	114
Other	137	141	411	423
Special items - merger-related costs	5	22	39	67
Special items—other	0	0	0	25
Total Operating Expenses	1,967	1,915	5,742	5,603
Operating Income	422	297	811	597
Nonoperating Income (Expense)
Interest income	11	11	31	29
Interest expense	(18)	(22)	(60)	(71)
Interest capitalized	4	5	11	14
Other—net	(3)	(7)	(20)	(20)
Nonoperating Income (Expense) Total	(6)	(13)	(38)	(48)
Income Before Income Tax	416	284	773	549
Income tax expense	94	67	185	135
Net Income	$ 322	$ 217	$ 588	$ 414
Basic Earnings Per Share (usd per share)	$ 2.61	$ 1.76	$ 4.76	$ 3.36
Diluted Earnings Per Share (usd per share)	$ 2.60	$ 1.75	$ 4.74	$ 3.34
Shares used for computation:
Basic shares (shares)	123,280	123,224	123,330	123,216
Diluted shares (shares)	124,067	123,864	124,051	123,804
Passenger Revenue [Member]
Operating Revenues
Revenue from Contract with Customer, Excluding Assessed Tax	$ 2,211	$ 2,043	$ 6,038	$ 5,724
Passenger Revenue [Member] | Passenger [Member]
Operating Revenues
Revenue from Contract with Customer, Excluding Assessed Tax	2,211	2,043	6,038	5,724
Mileage Plan Revenue [Member]
Operating Revenues
Revenue from Contract with Customer, Excluding Assessed Tax	304	267	857	788
Mileage Plan Revenue [Member] | Passenger [Member]
Operating Revenues
Revenue from Contract with Customer, Excluding Assessed Tax	186	153	511	459
Mileage Plan Revenue [Member] | Mileage plan other revenue [Member]
Operating Revenues
Revenue from Contract with Customer, Excluding Assessed Tax	118	114	346	329
Cargo and Other Revenue [Member]
Operating Revenues
Revenue from Contract with Customer, Excluding Assessed Tax	60	55	169	147
Cargo and Other Revenue [Member] | Cargo and Freight [Member]
Operating Revenues
Revenue from Contract with Customer, Excluding Assessed Tax	$ 60	$ 55	$ 169	$ 147