OPERATING SEGMENT INFORMATION (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016		Dec. 31, 2015
Operating revenues
Passenger, Mainline		$ 5,858	$ 4,098		$ 3,939
Passenger, Regional		960	908		854
Total passenger revenue		6,818	5,006		4,793
CPA revenues		0	0		0
Freight and mail		114	108		108
Other Net and Special Revenue		1,001	817		697
Total Operating Revenues		7,933	5,931		5,598
Operating expenses
Operating expenses, excluding fuel		5,226	3,751		3,346
Special items—merger-related costs and other		118	117
Economic fuel		1,447	831		954
Total Operating Expenses		6,673	4,582		4,300
Nonoperating Income (Expense)
Interest income		34	27		21
Interest expense		(103)	(55)		(42)
Other		16	24		35
Nonoperating Income (Expense) Total		(53)	(4)		14
Income (loss) before income tax		1,207	1,345		1,312
Depreciation		372	363		320
Capital expenditures		1,026	678		831
Total assets		10,740	9,962
Air Group Adjusted [Member]
Operating revenues
Passenger, Mainline	[1]	5,858	4,098		3,939
Passenger, Regional	[1]	960	908		854
Total passenger revenue	[1]	6,818	5,006		4,793
CPA revenues	[1]	0	0		0
Freight and mail	[1]	114	108		108
Other Net and Special Revenue	[1]	1,001	817		697
Total Operating Revenues	[1]	7,933	5,931		5,598
Operating expenses
Operating expenses, excluding fuel	[1]	5,108	3,634		3,314
Economic fuel	[1]	1,454	844		954
Total Operating Expenses	[1]	6,562	4,478		4,268
Nonoperating Income (Expense)
Interest income	[1]	34	27		21
Interest expense	[1]	(103)	(55)		(42)
Other	[1]	16	24		35
Nonoperating Income (Expense) Total	[1]	(53)	(4)		14
Income (loss) before income tax	[1]	1,318	1,449		1,344
Alaska Mainline [Member]
Operating revenues
Passenger, Mainline		5,858	4,098		3,939
Passenger, Regional		0	0		0
Total passenger revenue		5,858	4,098		3,939
CPA revenues		0	0		0
Freight and mail		110	104		103
Other Net and Special Revenue		922	738		621
Total Operating Revenues		6,890	4,940		4,663
Operating expenses
Operating expenses, excluding fuel		4,257	2,883		2,653
Economic fuel		1,282	719		823
Total Operating Expenses		5,539	3,602		3,476
Nonoperating Income (Expense)
Interest income		39	26		19
Interest expense		(92)	(42)		(28)
Other		14	19		28
Nonoperating Income (Expense) Total		(39)	3		19
Income (loss) before income tax		1,312	1,341		1,206
Depreciation	[2]	308	296		268
Capital expenditures	[2]	734	608		821
Total assets	[2]	16,650	15,260
Alaska Regional [Member]
Operating revenues
Passenger, Mainline		0	0		0
Passenger, Regional		960	908		854
Total passenger revenue		960	908		854
CPA revenues		0	0		0
Freight and mail		4	5		5
Other Net and Special Revenue		74	74		72
Total Operating Revenues		1,038	987		931
Operating expenses
Operating expenses, excluding fuel		851	769		695
Economic fuel		172	125		131
Total Operating Expenses		1,023	894		826
Nonoperating Income (Expense)
Interest income		0	0		0
Interest expense		0	0		0
Other		0	0		0
Nonoperating Income (Expense) Total		0	0		0
Income (loss) before income tax		15	93		105
Horizon [Member]
Operating revenues
Passenger, Mainline		0	0		0
Passenger, Regional		0	0		0
Total passenger revenue		0	0		0
CPA revenues		426	424		408
Freight and mail		0	0		0
Other Net and Special Revenue		4	4		4
Total Operating Revenues		430	428		412
Operating expenses
Operating expenses, excluding fuel		427	407		375
Economic fuel		0	0		0
Total Operating Expenses		427	407		375
Nonoperating Income (Expense)
Interest income		0	1		0
Interest expense		(13)	(9)		(10)
Other		2	1		1
Nonoperating Income (Expense) Total		(11)	(7)		(9)
Income (loss) before income tax		(8)	14		28
Depreciation		64	67		52
Capital expenditures		292	70		10
Total assets		929	690
Parent [Member]
Nonoperating Income (Expense)
Total assets		(6,839)	(5,988)
Intersegment Eliminations
Operating revenues
Passenger, Mainline		0	0		0
Passenger, Regional		0	0		0
Total passenger revenue		0	0		0
CPA revenues		(426)	(424)		(408)
Freight and mail		0	(1)		0
Other Net and Special Revenue		1	1		0
Total Operating Revenues		(425)	(424)		(408)
Operating expenses
Operating expenses, excluding fuel		(427)	(425)		(409)
Economic fuel		0	0		0
Total Operating Expenses		(427)	(425)		(409)
Nonoperating Income (Expense)
Interest income		(5)	0		2
Interest expense		2	(4)		(4)
Other		0	4		6
Nonoperating Income (Expense) Total		(3)	0		4
Income (loss) before income tax		(1)	1		5
Special Charges [Member]
Operating revenues
Passenger, Mainline	[3]	0	0		0
Passenger, Regional	[3]	0	0		0
Total passenger revenue	[3]	0	0		0
CPA revenues	[3]	0	0		0
Freight and mail	[3]	0	0		0
Other Net and Special Revenue	[3]	0	0		0
Total Operating Revenues	[3]	0	0		0
Operating expenses
Operating expenses, excluding fuel		118	117	[3]	32	[3]
Economic fuel		(7)	(13)	[3]	0	[3]
Total Operating Expenses	[3]	111	104		32
Nonoperating Income (Expense)
Interest income	[3]	0	0		0
Interest expense	[3]	0	0		0
Other	[3]	0	0		0
Nonoperating Income (Expense) Total	[3]	0	0		0
Income (loss) before income tax	[3]	$ (111)	$ (104)		$ (32)

[1] Year Ended December 31, 2015Mainline Regional Horizon Consolidating & Other(b) Air Group Adjusted(c) Special Items(d) ConsolidatedOperating revenues Passenger Mainline$3,939 $— $— $— $3,939 $— $3,939Regional— 854 — — 854 — 854Total passenger revenues3,939 854 — — 4,793 — 4,793CPA revenues— — 408 (408) — — —Freight and mail103 5 — — 108 — 108Other-net621 72 4 — 697 — 697Total operating revenues4,663 931 412 (408) 5,598 — 5,598 Operating expenses Operating expenses, excluding fuel2,653 695 375 (409) 3,314 32 3,346Fuel expense823 131 — — 954 — 954Total operating expenses3,476 826 375 (409) 4,268 32 4,300 Nonoperating income (expense) Interest income19 — — 2 21 — 21Interest expense(28) — (10) (4) (42) — (42)Other28 — 1 6 35 — 35 19 — (9) 4 14 — 14Income (loss) before income tax$1,206 $105 $28 $5 $1,344 $(32) $1,312

[2] 2017 2016 2015Depreciation and amortization: Mainline$308 $296 $268Horizon64 67 52Consolidated$372 $363 $320 Capital expenditures: Mainline$734 $608 $821Horizon292 70 10Consolidated$1,026 $678 $831 Total assets at end of period: Mainline$16,650 $15,260 Horizon929 690 Consolidating & Other(6,839) (5,988) Consolidated$10,740 $9,962

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