OPERATING SEGMENT INFORMATION (Tables) - USD ($)
$ in Millions

3 Months Ended

9 Months Ended

Sep. 30, 2021

Sep. 30, 2020

Sep. 30, 2021

Sep. 30, 2020

Segment Reporting [Abstract]

Schedule of Segment Reporting Information, by Segment

Operating segment information is as follows (in millions):

	Three Months Ended September 30, 2021
	Mainline		Regional		Horizon		Consolidating & Other(a)		Air Group Adjusted(b)		Special Items(c)		Consolidated
Operating Revenues
Passenger revenues	$	1,425	$	349	$	—	$	—	$	1,774	$	—	$	1,774
CPA revenues	—		—		107		(107)		—		—		—
Mileage Plan other revenue	105		15		—		—		120		—		120
Cargo and other	58		—		—		1		59		—		59
Total Operating Revenues	1,588		364		107		(106)		1,953		—		1,953
Operating Expenses
Operating expenses, excluding fuel	1,060		288		93		(113)		1,328		(9)		1,319
Economic fuel	299		77		—		—		376		—		376
Total Operating Expenses	1,359		365		93		(113)		1,704		(9)		1,695
Nonoperating Income (Expense)
Interest income	7		—		—		(1)		6		—		6
Interest expense	(25)		—		(6)		1		(30)		—		(30)
Interest capitalized	2		—		—		1		3		—		3
Other - net	8		—		—		—		8		—		8
Total Nonoperating Income (Expense)	(8)		—		(6)		1		(13)		—		(13)
Income (Loss) Before Income Tax	$	221	$	(1)	$	8	$	8	$	236	$	9	$	245
	Three Months Ended September 30, 2020
	Mainline		Regional		Horizon		Consolidating & Other(a)		Air Group Adjusted(b)		Special Items(c)		Consolidated
Operating Revenues
Passenger revenues	$	401	$	171	$	—	$	—	$	572	$	—	$	572
CPA revenues	—		—		95		(95)		—		—		—
Mileage Plan other revenue	65		19		—		—		84		—		84
Cargo and other	45		—		—		—		45		—		45
Total Operating Revenues	511		190		95		(95)		701		—		701
Operating Expenses
Operating expenses, excluding fuel	872		248		78		(97)		1,101		46		1,147
Economic fuel	90		38		—		—		128		(3)		125
Total Operating Expenses	962		286		78		(97)		1,229		43		1,272
Nonoperating Income (Expense)
Interest income	8		—		—		(1)		7		—		7
Interest expense	(28)		—		(6)		—		(34)		—		(34)
Interest capitalized	4		—		—		—		4		—		4
Other - net	4		—		—		1		5		—		5
Total Nonoperating Income (Expense)	(12)		—		(6)		—		(18)		—		(18)
Income (Loss) Before Income Tax	$	(463)	$	(96)	$	11	$	2	$	(546)	$	(43)	$	(589)

	Nine Months Ended September 30, 2021
	Mainline		Regional		Horizon		Consolidating & Other(a)		Air Group Adjusted(b)		Special Items(c)		Consolidated
Operating Revenues
Passenger revenues	$	3,003	$	782	$	—	$	—	$	3,785	$	—	$	3,785
CPA revenues	—		—		322		(322)		—		—		—
Mileage Plan other revenue	287		45		—		—		332		—		332
Cargo and other	157		—		—		3		160		—		160
Total Operating Revenues	3,447		827		322		(319)		4,277		—		4,277
Operating Expenses
Operating expenses, excluding fuel	2,937		839		272		(349)		3,699		(921)		2,778
Economic fuel	726		195		—		—		921		(68)		853
Total Operating Expenses	3,663		1,034		272		(349)		4,620		(989)		3,631
Nonoperating Income (Expense)
Interest income	20		—		—		(1)		19		—		19
Interest expense	(86)		—		(16)		1		(101)		—		(101)
Interest capitalized	8		—		—		1		9		—		9
Other - net	27		—		—		—		27		—		27
Total Nonoperating Income (Expense)	(31)		—		(16)		1		(46)		—		(46)
Income (Loss) Before Income Tax	$	(247)	$	(207)	$	34	$	31	$	(389)	$	989	$	600
	Nine Months Ended September 30, 2020
	Mainline		Regional		Horizon		Consolidating & Other(a)		Air Group Adjusted(b)		Special Items(c)		Consolidated
Operating Revenues
Passenger revenues	$	1,860	$	502	$	—	$	—	$	2,362	$	—	$	2,362
CPA revenues	—		—		281		(281)		—		—		—
Mileage Plan other revenue	219		47		—		—		266		—		266
Cargo and other	128		—		—		2		130		—		130
Total Operating Revenues	2,207		549		281		(279)		2,758		—		2,758
Operating Expenses
Operating expenses, excluding fuel	2,777		727		238		(289)		3,453		(83)		3,370
Economic fuel	448		120		—		—		568		—		568
Total Operating Expenses	3,225		847		238		(289)		4,021		(83)		3,938
Nonoperating Income (Expense)
Interest income	33		—		—		(10)		23		—		23
Interest expense	(58)		—		(16)		10		(64)		—		(64)
Interest capitalized	8		—		—		—		8		—		8
Other - net	16		—		—		—		16		—		16
Total Nonoperating Income (Expense)	(1)		—		(16)		—		(17)		—		(17)
Income (Loss) Before Income Tax	$	(1,019)	$	(298)	$	27	$	10	$	(1,280)	$	83	$	(1,197)

(a)Includes consolidating entries, Air Group parent company, McGee Air Services, and other immaterial business units.

(b)The Air Group Adjusted column represents the financial information that is reviewed by management to assess performance of operations and determine capital allocation and excludes certain charges. See Note A in the accompanying pages for further information.

(c)Includes Payroll Support Program wage offsets, special items and mark-to-market fuel hedge accounting adjustments.

Total assets were as follows (in millions):

	September 30, 2021		December 31, 2020
Mainline	$	19,161	$	19,754
Horizon	1,251		1,170
Consolidating & Other	(6,530)		(6,878)
Consolidated	$	13,882	$	14,046

Nonoperating Income (Expense)

$ (13)

$ (18)

$ (46)

$ (17)

Interest income

6

7

19

23

Operating Expenses, Excluding Fuel

1,319

1,147

2,778

3,370

Economic fuel

376

125

853

568

Operating Expenses

1,695

1,272

3,631

3,938

Income (Loss) Before Income Tax

$ 245

$ (589)

$ 600

$ (1,197)