Amount of revenue recognized that was previously included in balance of obligation to transfer good or service to customer for which consideration from customer has been received or is due.

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Value of revenue deferred or cost to provide future services associated with points or miles outstanding and awards that expect to be redeemed through customer loyalty programs and the value of transportation services sold but as yet used by the passenger. Used to reflect the current portion of the liability (within one year or within the normal operating cycle if longer).

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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No definition available.

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The total amount due to the entity within one year of the balance sheet date (or one operating cycle, if longer) from outside sources, including trade accounts receivable, notes and loans receivable, as well as any other types of receivables, net of allowances established for the purpose of reducing such receivables to an amount that approximates their net realizable value.

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REVENUE FROM CONTRACTS WITH CUSTOMERS - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Deferred Revenue Arrangement [Line Items]
Air traffic liability	$ 1,173		$ 1,173		$ 788
Receivable	389		389		366
Mileage Plan Revenue [Member]
Deferred Revenue Arrangement [Line Items]
Receivable	122		122		$ 119
Mileage Plan Revenue [Member] \| Mileage plan other revenue [Member]
Deferred Revenue Arrangement [Line Items]
Contract liability revenue recognized			(51)	$ (44)
Passenger Revenue [Member]
Deferred Revenue Arrangement [Line Items]
Contract liability revenue recognized	$ 89	$ 79	$ 563	$ 513