OPERATING SEGMENT INFORMATION (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Operating Revenues
Total Operating Revenues	$ 1,527	$ 421	$ 2,324	$ 2,057
Operating expenses
Operating Expenses, Excluding Fuel	704	650	1,459	2,223
Economic fuel	274	59	477	443
Total Operating Expenses	978	709	1,936	2,666
Nonoperating Income (Expense)
Interest income	6	7	13	16
Interest expense	(39)	(17)	(71)	(30)
Interest Costs Capitalized	3	1	6	4
Other	9	6	19	11
Nonoperating Income (Expense) Total	(21)	(3)	(33)	1
Income (loss) before income tax	528	(291)	355	(608)
Costs and Expenses, Total	978	709	1,936	2,666
Interest Costs Incurred	39	17	71	30
Air Group Adjusted [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	1,527	421	2,324	2,057
Operating expenses
Operating Expenses, Excluding Fuel	1,234	942	2,371	2,352
Economic fuel	320	65	545	440
Total Operating Expenses	1,554	1,007	2,916	2,792
Nonoperating Income (Expense)
Interest income	6	7	13	16
Interest expense	(39)	(17)	(71)	(30)
Interest Costs Capitalized	3	1	6	4
Other	9	6	19	11
Nonoperating Income (Expense) Total	(21)	(3)	(33)	1
Income (loss) before income tax	(48)	(589)	(625)	(734)
Alaska Mainline [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	1,229	320	1,859	1,696
Operating expenses
Operating Expenses, Excluding Fuel	984	746	1,877	1,905
Economic fuel	253	45	427	358
Total Operating Expenses	1,237	791	2,304	2,263
Nonoperating Income (Expense)
Interest income	6	11	13	25
Interest expense	(34)	(18)	(61)	(30)
Interest Costs Capitalized	3	1	6	4
Other	9	6	19	12
Nonoperating Income (Expense) Total	(16)	0	(23)	11
Income (loss) before income tax	(24)	(471)	(468)	(556)
Alaska Regional [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	296	101	463	359
Operating expenses
Operating Expenses, Excluding Fuel	286	210	551	479
Economic fuel	66	20	118	82
Total Operating Expenses	352	230	669	561
Nonoperating Income (Expense)
Interest income	0	0	0	0
Interest expense	0	0	0	0
Interest Costs Capitalized	0	0	0	0
Other	0	0	0	0
Nonoperating Income (Expense) Total	0	0	0	0
Income (loss) before income tax	(56)	(129)	(206)	(202)
Horizon [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	111	81	215	186
Operating expenses
Operating Expenses, Excluding Fuel	91	68	179	160
Economic fuel	0	0	0	0
Total Operating Expenses	91	68	179	160
Nonoperating Income (Expense)
Interest income	0	0	0	0
Interest expense	(5)	(5)	(10)	(10)
Interest Costs Capitalized	0	0	0	0
Other	0	0	0	0
Nonoperating Income (Expense) Total	(5)	(5)	(10)	(10)
Income (loss) before income tax	15	8	26	16
Consolidating and Other [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	(109)	(81)	(213)	(184)
Operating expenses
Operating Expenses, Excluding Fuel	(127)	(82)	(236)	(192)
Economic fuel	1	0	0	0
Total Operating Expenses	(126)	(82)	(236)	(192)
Nonoperating Income (Expense)
Interest income	0	(4)	0	(9)
Interest expense	0	(6)	0	(10)
Interest Costs Capitalized	0	0	0	0
Other	0	0	0	(1)
Nonoperating Income (Expense) Total	0	2	0	0
Income (loss) before income tax	17	3	23	8
Special Charges [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	0	0	0	0
Operating expenses
Operating Expenses, Excluding Fuel	(530)	(292)	(912)	(129)
Economic fuel	(46)	(6)	(68)	3
Total Operating Expenses	(576)	(298)	(980)	(126)
Nonoperating Income (Expense)
Interest income	0	0	0	0
Interest expense	0	0	0	0
Interest Costs Capitalized	0	0	0	0
Other	0	0	0	0
Nonoperating Income (Expense) Total	0	0	0	0
Income (loss) before income tax	576	298	980	126
Passenger [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	1,352	309	2,011	1,790
Passenger [Member] | Air Group Adjusted [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	1,352	309	2,011	1,790
Passenger [Member] | Alaska Mainline [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	1,072	225	1,578	1,459
Passenger [Member] | Alaska Regional [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	280	84	433	331
Passenger [Member] | Horizon [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	0	0	0	0
Passenger [Member] | Consolidating and Other [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	0	0	0	0
Passenger [Member] | Special Charges [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	0	0	0	0
Capacity Purchase Agreements [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	0	0	0	0
Capacity Purchase Agreements [Member] | Air Group Adjusted [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	0	0	0	0
Capacity Purchase Agreements [Member] | Alaska Mainline [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	0	0	0	0
Capacity Purchase Agreements [Member] | Alaska Regional [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	0	0	0	0
Capacity Purchase Agreements [Member] | Horizon [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	111	81	215	186
Capacity Purchase Agreements [Member] | Consolidating and Other [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	(111)	(81)	(215)	(186)
Capacity Purchase Agreements [Member] | Special Charges [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	0	0	0	0
Mileage plan other revenue [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	118	73	212	182
Mileage plan other revenue [Member] | Air Group Adjusted [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	118	73	212	182
Mileage plan other revenue [Member] | Alaska Mainline [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	102	56	182	154
Mileage plan other revenue [Member] | Alaska Regional [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	16	17	30	28
Mileage plan other revenue [Member] | Horizon [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	0	0	0	0
Mileage plan other revenue [Member] | Consolidating and Other [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	0	0	0	0
Mileage plan other revenue [Member] | Special Charges [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	0	0	0	0
Cargo and Freight [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	57	39	101	85
Cargo and Freight [Member] | Air Group Adjusted [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	57	39	101	85
Cargo and Freight [Member] | Alaska Mainline [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	55	39	99	83
Cargo and Freight [Member] | Alaska Regional [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	0	0	0	0
Cargo and Freight [Member] | Horizon [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	0	0	0	0
Cargo and Freight [Member] | Consolidating and Other [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	2	0	2	2
Cargo and Freight [Member] | Special Charges [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	$ 0	$ 0	$ 0	$ 0