Comprehensive Income (Loss) - Schedule of AOCI Components (Details) $ in Millions	3 Months Ended
	Mar. 31, 2022 USD ($)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	$ 10,414
Changes in fair value	658
Reclassification to earnings	(155)
Balance at end of period	10,417
Accumulated other comprehensive income
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	388
Balance at end of period	891
Fuel and Interest Rate Derivatives | Fuel derivative contracts
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	492
Changes in fair value	852
Reclassification to earnings	(203)
Balance at end of period	1,141
Fuel and Interest Rate Derivatives | Interest rate derivatives
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	(57)
Changes in fair value	5
Reclassification to earnings	2
Balance at end of period	(50)
Defined benefit plan items
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	66
Balance at end of period	66
Deferred tax
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	(113)
Changes in fair value	(199)
Reclassification to earnings	46
Balance at end of period	$ (266)