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Revenue - Roll Forward of Frequent Flyer Deferred Revenue (Details) - Frequent Flyer - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2019 | Sep. 30, 2018 | Sep. 30, 2019 | Sep. 30, 2018
Frequent Flyer Deferred Revenue [Roll Forward] |  |  |  |
Total Frequent flyer deferred revenue - beginning balance | $ 5,198 | $ 4,989 | $ 5,005 | $ 4,783
Miles awarded | 662 | 616 | 1,951 | 1,826
Travel miles redeemed (Passenger revenue) | (607) | (580) | (1,634) | (1,508)
Non-travel miles redeemed (Other operating revenue) | (34) | (38) | (103) | (114)
Total Frequent flyer deferred revenue - ending balance | $ 5,219 | $ 4,987 | $ 5,219 | $ 4,987

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- Definition Amount of obligation to transfer good or service to customer for which consideration has been received or is receivable. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 606 -SubTopic 10 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=118944033&loc=SL49130531-203044 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 606 -SubTopic 10 -Section 50 -Paragraph 8 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130549-203045 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 606 -SubTopic 10 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=118944033&loc=SL49130532-203044 + Details
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