Condensed Consolidated Statement of Cash Flows - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income (loss)	$ 348	$ (915)	$ 463	$ (1,009)
Adjustments to reconcile net income (loss) to cash provided by operating activities:
Depreciation and amortization	315	313	627	624
Unrealized/realized (gain) loss on fuel derivative instruments	(17)	6	(23)	8
Deferred income taxes	(30)	(181)	(26)	(230)
Gain on sale-leaseback transactions	0	(222)	0	(222)
Changes in certain assets and liabilities:
Accounts and other receivables	(563)	(119)	(797)	64
Other assets	16	224	5	282
Accounts payable and accrued liabilities	989	1,200	923	(90)
Air traffic liability	946	667	1,546	1,368
Other liabilities	(64)	(74)	(186)	(206)
Cash collateral received from derivative counterparties	48	12	86	7
Other, net	17	(14)	32	(76)
Net cash provided by operating activities	2,005	897	2,650	520
CASH FLOWS FROM INVESTING ACTIVITIES:
Capital expenditures	(95)	(113)	(190)	(336)
Supplier proceeds	0	128	0	428
Proceeds from sale-leaseback transactions	0	815	0	815
Purchases of short-term investments	(1,651)	(1,316)	(2,975)	(2,345)
Proceeds from sales of short-term and other investments	1,277	818	2,495	1,765
Net cash provided by (used in) investing activities	(469)	332	(670)	327
CASH FLOWS FROM FINANCING ACTIVITIES:
Issuance of common stock	0	2,294	0	2,294
Proceeds from issuance of long-term debt	0	3,997	0	4,497
Proceeds from term loan credit facility	0	2,683	0	3,683
Proceeds from revolving credit facility	0	0	0	1,000
Proceeds from convertible notes	0	2,300	0	2,300
Proceeds from Payroll Support Program loan and warrants	625	885	1,136	885
Proceeds from Employee stock plans	13	13	26	24
Repurchase of common stock	0	0	0	(451)
Payments of long-term debt and finance lease obligations	(43)	(159)	(109)	(237)
Payments of term loan credit facility	0	(3,683)	0	(3,683)
Payments of revolving credit facility	0	(1,000)	0	(1,000)
Payments of cash dividends	0	0	0	(188)
Capitalized financing items	0	(171)	0	(176)
Other, net	22	23	28	8
Net cash provided by financing activities	617	7,182	1,081	8,956
NET CHANGE IN CASH AND CASH EQUIVALENTS	2,153	8,411	3,061	9,803
CASH AND CASH EQUIVALENTS AT BEGINNING OF PERIOD	11,971	3,940	11,063	2,548
CASH AND CASH EQUIVALENTS AT END OF PERIOD	14,124	12,351	14,124	12,351
CASH PAYMENTS FOR:
Interest, net of amount capitalized	150	40	167	54
Income taxes	176	5	177	10
SUPPLEMENTAL DISCLOSURE OF NONCASH TRANSACTIONS:
Right-of-use assets acquired under operating leases	12	661	230	686
Flight equipment acquired against supplier credit memo	207	0	512	0
Assets constructed for others	$ (341)	$ 41	$ (309)	$ 75