REVENUE RECOGNITION - Loyalty Program Liability (Details) - Loyalty program - USD ($) $ in Millions	9 Months Ended
Sep. 30, 2023	Sep. 30, 2022
Loyalty program activity
Current and noncurrent deferred revenue, beginning	$ 7,882	$ 7,559
Miles earned	3,164	2,496
Miles redeemed for air travel	(2,547)	(2,073)
Miles redeemed for non-air travel and other	(126)	(122)
Current and noncurrent deferred revenue, ending	$ 8,373	$ 7,860

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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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant