Revenue - Summary of Passenger Revenue by Geographic Region and by Mainline Versus Regional (Details) - USD ($) $ in Millions	3 Months Ended			9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017		Sep. 30, 2018	Sep. 30, 2017
Disaggregation of Revenue [Line Items]
Revenue	$ 11,003	$ 9,899	[1]	$ 30,812	$ 28,333	[2]
Passenger revenue
Disaggregation of Revenue [Line Items]
Revenue	10,120	9,069	[1]	28,150	25,873	[2]
Passenger revenue | International
Disaggregation of Revenue [Line Items]
Revenue	3,867	3,626		10,747	10,121
Passenger revenue | Domestic
Disaggregation of Revenue [Line Items]
Revenue	6,253	5,443		17,403	15,752
Passenger revenue | Atlantic
Disaggregation of Revenue [Line Items]
Revenue	1,933	1,724		5,009	4,456
Passenger revenue | Pacific
Disaggregation of Revenue [Line Items]
Revenue	1,163	1,125		3,335	3,242
Passenger revenue | Latin America
Disaggregation of Revenue [Line Items]
Revenue	$ 771	$ 777		$ 2,403	$ 2,423

[1] Amounts adjusted due to the adoption of Accounting Standards Update No. 2014-09, Revenue from Contracts with Customers (Topic 606) and Accounting Standards Update No. 2017-07, Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost. See Note 1 to the financial statements contained in Part I, Item 1 of this report for additional information.

[2] Amounts adjusted due to the adoption of Accounting Standards Update No. 2014-09, Revenue from Contracts with Customers (Topic 606) and Accounting Standards Update No. 2017-07, Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost. See Note 1 to the financial statements contained in Part I, Item 1 of this report for additional information.