Comprehensive Income (Loss) - Schedule of AOCI Components (Details) $ in Millions	3 Months Ended
	Mar. 31, 2023 USD ($)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	$ 10,687
Changes in fair value	(127)
Reclassification to earnings	(20)
Balance at end of period	10,302
Accumulated other comprehensive income
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	344
Balance at end of period	197
Fuel and Interest Rate Derivatives | Fuel derivative contracts
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	305
Changes in fair value	(163)
Reclassification to earnings	(28)
Balance at end of period	114
Fuel and Interest Rate Derivatives | Interest rate derivatives
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	(32)
Changes in fair value	(2)
Reclassification to earnings	2
Balance at end of period	(32)
Defined benefit plan items
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	170
Balance at end of period	170
Deferred tax impact
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	(99)
Changes in fair value	38
Reclassification to earnings	6
Balance at end of period	$ (55)