REVENUE RECOGNITION - Loyalty Program Liability (Details) - Loyalty program - USD ($) $ in Millions	6 Months Ended
Jun. 30, 2024	Jun. 30, 2023
Loyalty program activity
Current and noncurrent deferred revenue, beginning	$ 8,420	$ 7,882
Miles earned	2,148	2,110
Miles redeemed for air travel	(1,820)	(1,645)
Miles redeemed for non-air travel and other	(114)	(80)
Current and noncurrent deferred revenue, ending	$ 8,634	$ 8,267

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