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

3 Months Ended

Mar. 31, 2021

Mar. 31, 2020

Segment Reporting [Abstract]

Schedule of Segment Reporting Information, by Segment

Operating segment information is as follows (in millions):

	Three Months Ended March 31, 2021
	Mainline		Regional		Horizon		Consolidating & Other(a)		Air Group Adjusted(b)		Special Items(c)		Consolidated
Operating Revenues
Passenger revenues	$	506	$	153	$	—	$	—	$	659	$	—	$	659
CPA revenues	—		—		104		(104)		—		—		—
Mileage Plan other revenue	80		14		—		—		94		—		94
Cargo and other	44		—		—		—		44		—		44
Total Operating Revenues	630		167		104		(104)		797		—		797
Operating Expenses
Operating expenses, excluding fuel	893		265		88		(109)		1,137		(382)		755
Economic fuel	174		52		—		(1)		225		(22)		203
Total Operating Expenses	1,067		317		88		(110)		1,362		(404)		958
Nonoperating Income (Expense)
Interest income	7		—		—		—		7		—		7
Interest expense	(27)		—		(5)		—		(32)		—		(32)
Interest capitalized	3		—		—		—		3		—		3
Other - net	10		—		—		—		10		—		10
Total Nonoperating Income (Expense)	(7)		—		(5)		—		(12)		—		(12)
Income (Loss) Before Income Tax	$	(444)	$	(150)	$	11	$	6	$	(577)	$	404	$	(173)
	Three Months Ended March 31, 2020
	Mainline		Regional		Horizon		Consolidating & Other(a)		Air Group Adjusted(b)		Special Items(c)		Consolidated
Operating Revenues
Passenger revenues	$	1,234	$	247	$	—	$	—	$	1,481	$	—	$	1,481
CPA revenues	—		—		105		(105)		—		—		—
Mileage Plan other revenue	98		11		—		—		109		—		109
Cargo and other	44		—		—		2		46		—		46
Total Operating Revenues	1,376		258		105		(103)		1,636		—		1,636
Operating Expenses
Operating expenses, excluding fuel	1,159		269		92		(110)		1,410		163		1,573
Economic fuel	313		62		—		—		375		9		384
Total Operating Expenses	1,472		331		92		(110)		1,785		172		1,957
Nonoperating Income (Expense)
Interest income	14		—		—		(5)		9		—		9
Interest expense	(12)		—		(5)		4		(13)		—		(13)
Interest capitalized	3		—		—		—		3		—		3
Other - net	6		—		—		(1)		5		—		5
Total Nonoperating Income (Expense)	11		—		(5)		(2)		4		—		4
Income (Loss) Before Income Tax	$	(85)	$	(73)	$	8	$	5	$	(145)	$	(172)	$	(317)

(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):

	March 31, 2021		December 31, 2020
Mainline	$	19,951	$	19,754
Horizon	1,200		1,170
Consolidating & Other	(6,889)		(6,878)
Consolidated	$	14,262	$	14,046

Revenues

$ 797

$ 1,636

Income (Loss) Before Income Tax

(173)

(317)

Nonoperating Income (Expense)

(12)

4

Interest income

7

9

Interest expense

(32)

(13)

Interest Costs Capitalized

3

3

Other

10

5

Operating Expenses, Excluding Fuel

755

1,573

Economic fuel

203

384

Operating Expenses

$ 958

$ 1,957