Comprehensive Income (Loss) - Schedule of AOCI Components (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	$ 8,876	$ 9,832	$ 9,853
Changes in fair value	547	(129)
Reclassification to earnings	(34)	85
Balance at end of period	$ 10,414	8,876	$ 9,832
Accounting Standards Update [Extensible Enumeration]	Accounting Standards Update 2016-01 [Member]		Accounting Standards Update 2016-02 [Member]
Cumulative Effect, Period of Adoption, Adjustment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	$ 0		$ 55
Balance at end of period		0
Accumulated other comprehensive income (loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	(105)	(61)	20
Balance at end of period	388	(105)	(61)
Accumulated other comprehensive income (loss) | Cumulative Effect, Period of Adoption, Adjustment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	(20)
Balance at end of period		(20)
Fuel derivatives | Fuel derivative contracts
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	(119)	(125)
Changes in fair value	601	(103)
Reclassification to earnings	10	109
Balance at end of period	492	(119)	(125)
Fuel derivatives | Interest rate derivatives
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	(66)	(33)
Changes in fair value	3	(34)
Reclassification to earnings	6	1
Balance at end of period	(57)	(66)	(33)
Defined benefit plan items
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	(43)	20
Changes in fair value	109	(63)
Balance at end of period	66	(43)	20
Other
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	91	59
Changes in fair value		32
Balance at end of period	0	91	59
Other | Cumulative Effect, Period of Adoption, Adjustment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	(31)
Balance at end of period		(31)
Other | Fuel derivative contracts
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Reclassification to earnings	(60)
Deferred tax impact
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	32	18
Changes in fair value	(166)	39
Reclassification to earnings	10	(25)
Balance at end of period	(113)	32	$ 18
Deferred tax impact | Cumulative Effect, Period of Adoption, Adjustment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	$ 11
Balance at end of period		$ 11