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REVENUE RECOGNITION - Roll Forward of Frequent Flyer Deferred Revenue (Details) - Frequent Flyer Program - USD ($) $ in Millions | 3 Months Ended
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Mar. 31, 2025 | Mar. 31, 2024
Frequent Flyer Deferred Revenue [Roll Forward] |  |
Balance at January 1 | $ 7,441 | $ 7,143
Miles earned | 919 | 840
Travel miles redeemed | (730) | (665)
Non-travel miles redeemed | (38) | (39)
Balance at March 31 | $ 7,591 | $ 7,279

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- Details
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