Comprehensive Income - Schedule of Components of Net Income and Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2026	Mar. 31, 2026	Jun. 30, 2025	Mar. 31, 2025	Jun. 30, 2026	Jun. 30, 2025
Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract]
Net income	$ 233		$ 213		$ 460	$ 64
Unrealized gain (loss) on fuel derivative instruments, net of deferred taxes	22		(12)		44	(12)
Other, net of deferred taxes	1		1		2	2
Total other comprehensive income (loss)	23		(11)		46	(10)
COMPREHENSIVE INCOME	256	$ 250	202	$ (148)	506	54
Derivative deferred taxes	7		(4)		14	(4)
Other deferred taxes	$ 0		$ 1		$ 0	$ 1

Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income and other comprehensive income, attributable to parent entity. Excludes changes in equity resulting from investments by owners and distributions to owners.

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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+ Details