Significant Accounting Policies - Information about Goodwill and Other Intangible Assets (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Accounting Policies [Abstract]
Goodwill	$ 4,527	$ 4,527
Indefinite-lived Intangible Assets [Line Items]
Gross  Carrying Amount	2,591	2,591
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	1,629	1,643
Accumulated Amortization	1,495	1,472
China route authority
Indefinite-lived Intangible Assets [Line Items]
Gross  Carrying Amount	1,020	1,020
Airport slots
Indefinite-lived Intangible Assets [Line Items]
Gross  Carrying Amount	574	574
Tradenames and logos
Indefinite-lived Intangible Assets [Line Items]
Gross  Carrying Amount	593	593
Alliances
Indefinite-lived Intangible Assets [Line Items]
Gross  Carrying Amount	404	404
Frequent flyer database
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	1,177	1,177
Accumulated Amortization	1,068	1,040
Hubs
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	145	145
Accumulated Amortization	131	124
Contracts
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	0	7
Accumulated Amortization	0	7
Other
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	307	314
Accumulated Amortization	$ 296	$ 301