Goodwill and Other Intangible Assets - Information about Goodwill and Other Intangible Assets (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill	$ 4,523	$ 4,523	[1]
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	1,756	1,757
Accumulated amortization	1,380	1,313	[1]
Indefinite-lived Intangible Assets [Line Items]
Gross carrying amount	2,783	3,095
Route authorities
Indefinite-lived Intangible Assets [Line Items]
Gross carrying amount	1,240	1,562
Airport slots and gates
Indefinite-lived Intangible Assets [Line Items]
Gross carrying amount	546	536
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	884	832
Hubs
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	145	145
Accumulated amortization	97	89
Contracts
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	120	121
Accumulated amortization	106	103
Patents and tradenames
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	108	108
Accumulated amortization	108	108
Airport slots and gates
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	97	97
Accumulated amortization	97	97
Other
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	109	109
Accumulated amortization	$ 88	$ 84

[1] Amounts adjusted due to the adoption of Accounting Standards Update No. 2014-09, Revenue from Contracts with Customers (Topic 606). See Note 1 to the financial statements contained in Part II, Item 8 of this report for additional information.