REVENUE RECOGNITION - Roll Forward of Frequent Flyer Deferred Revenue (Details) - Frequent Flyer Program - USD ($) $ in Millions	3 Months Ended
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

Amount of obligation to transfer good or service to customer for which consideration has been received or is receivable.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479837/606-10-45-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 8
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479806/606-10-50-8

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479837/606-10-45-2

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant