OPERATING SEGMENT INFORMATION (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Operating Revenues
Total Operating Revenues	$ 797	$ 1,636
Operating expenses
Operating Expenses, Excluding Fuel	755	1,573
Economic fuel	203	384
Total Operating Expenses	958	1,957
Nonoperating Income (Expense)
Interest income	7	9
Interest expense	(32)	(13)
Interest Costs Capitalized	3	3
Other	10	5
Nonoperating Income (Expense) Total	(12)	4
Income (loss) before income tax	(173)	(317)
Costs and Expenses, Total	958	1,957
Interest Costs Incurred	32	13
Air Group Adjusted [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	797	1,636
Operating expenses
Operating Expenses, Excluding Fuel	1,137	1,410
Economic fuel	225	375
Total Operating Expenses	1,362	1,785
Nonoperating Income (Expense)
Interest income	7	9
Interest expense	(32)	(13)
Interest Costs Capitalized	3	3
Other	10	5
Nonoperating Income (Expense) Total	(12)	4
Income (loss) before income tax	(577)	(145)
Alaska Mainline [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	630	1,376
Operating expenses
Operating Expenses, Excluding Fuel	893	1,159
Economic fuel	174	313
Total Operating Expenses	1,067	1,472
Nonoperating Income (Expense)
Interest income	7	14
Interest expense	(27)	(12)
Interest Costs Capitalized	3	3
Other	10	6
Nonoperating Income (Expense) Total	(7)	11
Income (loss) before income tax	(444)	(85)
Alaska Regional [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	167	258
Operating expenses
Operating Expenses, Excluding Fuel	265	269
Economic fuel	52	62
Total Operating Expenses	317	331
Nonoperating Income (Expense)
Interest income	0	0
Interest expense	0	0
Interest Costs Capitalized	0	0
Other	0	0
Nonoperating Income (Expense) Total	0	0
Income (loss) before income tax	(150)	(73)
Horizon [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	104	105
Operating expenses
Operating Expenses, Excluding Fuel	88	92
Economic fuel	0	0
Total Operating Expenses	88	92
Nonoperating Income (Expense)
Interest income	0	0
Interest expense	(5)	(5)
Interest Costs Capitalized	0	0
Other	0	0
Nonoperating Income (Expense) Total	(5)	(5)
Income (loss) before income tax	11	8
Consolidating and Other [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	(104)	(103)
Operating expenses
Operating Expenses, Excluding Fuel	(109)	(110)
Economic fuel	(1)	0
Total Operating Expenses	(110)	(110)
Nonoperating Income (Expense)
Interest income	0	(5)
Interest expense	0	(4)
Interest Costs Capitalized	0	0
Other	0	(1)
Nonoperating Income (Expense) Total	0	(2)
Income (loss) before income tax	6	5
Special Charges [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	0	0
Operating expenses
Operating Expenses, Excluding Fuel	(382)	163
Economic fuel	(22)	9
Total Operating Expenses	(404)	172
Nonoperating Income (Expense)
Interest income	0	0
Interest expense	0	0
Interest Costs Capitalized	0	0
Other	0	0
Nonoperating Income (Expense) Total	0	0
Income (loss) before income tax	404	(172)
Passenger [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	659	1,481
Passenger [Member] | Air Group Adjusted [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	659	1,481
Passenger [Member] | Alaska Mainline [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	506	1,234
Passenger [Member] | Alaska Regional [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	153	247
Passenger [Member] | Horizon [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	0	0
Passenger [Member] | Consolidating and Other [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	0	0
Passenger [Member] | Special Charges [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	0	0
Capacity Purchase Agreements [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	0	0
Capacity Purchase Agreements [Member] | Air Group Adjusted [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	0	0
Capacity Purchase Agreements [Member] | Alaska Mainline [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	0	0
Capacity Purchase Agreements [Member] | Alaska Regional [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	0	0
Capacity Purchase Agreements [Member] | Horizon [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	104	105
Capacity Purchase Agreements [Member] | Consolidating and Other [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	(104)	(105)
Capacity Purchase Agreements [Member] | Special Charges [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	0	0
Mileage plan other revenue [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	94	109
Mileage plan other revenue [Member] | Air Group Adjusted [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	94	109
Mileage plan other revenue [Member] | Alaska Mainline [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	80	98
Mileage plan other revenue [Member] | Alaska Regional [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	14	11
Mileage plan other revenue [Member] | Horizon [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	0	0
Mileage plan other revenue [Member] | Consolidating and Other [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	0	0
Mileage plan other revenue [Member] | Special Charges [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	0	0
Cargo and Freight [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	44	46
Cargo and Freight [Member] | Air Group Adjusted [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	44	46
Cargo and Freight [Member] | Alaska Mainline [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	44	44
Cargo and Freight [Member] | Alaska Regional [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	0	0
Cargo and Freight [Member] | Horizon [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	0	0
Cargo and Freight [Member] | Consolidating and Other [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	0	2
Cargo and Freight [Member] | Special Charges [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	$ 0	$ 0