REVENUE - Loyalty Program Revenue (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Disaggregation of Revenue [Line Items]
Revenue	$ 11,735	$ 10,426	$ 9,646
Mileage Plan Revenue
Disaggregation of Revenue [Line Items]
Revenue	1,913	1,682	1,521
Passenger \| Mileage Plan Revenue
Disaggregation of Revenue [Line Items]
Revenue	1,180	1,034	931
Mileage Plan Services, Other \| Mileage Plan Revenue
Disaggregation of Revenue [Line Items]
Revenue	$ 733	$ 648	$ 590

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

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+ Details