Comprehensive Income - Schedule of AOCI Components (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2024	Sep. 30, 2024
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	$ 10,465	$ 10,515
Changes in fair value	(61)	(83)
Reclassification to earnings	13	46
Balance at end of period	10,411	10,411
Accumulated other comprehensive income (loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	11	0
Balance at end of period	(37)	(37)
Fuel derivatives | Fuel derivatives
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	(125)	(135)
Changes in fair value	(79)	(108)
Reclassification to earnings	15	54
Balance at end of period	(189)	(189)
Defined benefit plan items
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	149	149
Changes in fair value	0	0
Reclassification to earnings	0	0
Balance at end of period	149	149
Other
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	(11)	(15)
Changes in fair value	0	0
Reclassification to earnings	2	6
Balance at end of period	(9)	(9)
Deferred tax impact
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	(2)	1
Changes in fair value	18	25
Reclassification to earnings	(4)	(14)
Balance at end of period	$ 12	$ 12