Condensed Consolidated Statement of Cash Flows - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income (loss)	$ 446	$ (1,157)	$ 909	$ (2,166)
Adjustments to reconcile net income (loss) to cash provided by (used in) operating activities:
Depreciation and amortization	322	315	949	940
Unrealized/realized (gain) loss on fuel derivative instruments	(2)	17	(25)	25
Deferred income taxes	67	(298)	42	(528)
Gain on sale-leaseback transactions	0	0	0	(222)
Loss on partial extinguishment of convertible notes	12	0	12	0
Changes in certain assets and liabilities:
Accounts and other receivables	(23)	(123)	(819)	(60)
Other assets	59	84	64	366
Accounts payable and accrued liabilities	(948)	26	(25)	(65)
Air traffic liability	(442)	216	1,103	1,584
Other liabilities	(88)	(106)	(275)	(312)
Cash collateral received from (provided to) derivative counterparties	42	(5)	128	2
Other, net	(20)	(19)	12	(95)
Net cash provided by (used in) operating activities	(575)	(1,050)	2,075	(531)
CASH FLOWS FROM INVESTING ACTIVITIES:
Capital expenditures	(135)	(89)	(325)	(425)
Supplier proceeds	0	0	0	428
Assets constructed for others	(3)	0	(3)	0
Proceeds from sale-leaseback transactions	0	0	0	815
Purchases of short-term investments	(1,525)	(1,536)	(4,500)	(3,881)
Proceeds from sales of short-term and other investments	1,251	1,191	3,747	2,956
Net cash used in investing activities	(412)	(434)	(1,081)	(107)
CASH FLOWS FROM FINANCING ACTIVITIES:
Issuance of common stock	0	0	0	2,294
Proceeds from issuance of long-term debt	0	1,125	0	5,622
Proceeds from term loan credit facility	0	0	0	3,683
Proceeds from revolving credit facility	0	0	0	1,000
Proceeds from convertible notes	0	0	0	2,300
Proceeds from Payroll Support Program loan and warrants	0	130	1,136	1,016
Proceeds from Employee stock plans	13	13	39	36
Repurchase of common stock	0	0	0	(451)
Payments of long-term debt and finance lease obligations	(67)	(59)	(177)	(295)
Payments of term loan credit facility	0	0	0	(3,683)
Payments of revolving credit facility	0	0	0	(1,000)
Payments of cash dividends	0	0	0	(188)
Payments of terminated interest rate derivative instruments	0	(31)	0	(31)
Payments for repurchases and conversions of convertible debt	(121)	0	(121)	0
Capitalized financing items	0	44	0	(133)
Other, net	18	20	46	29
Net cash provided by (used in) financing activities	(157)	1,242	923	10,199
NET CHANGE IN CASH AND CASH EQUIVALENTS	(1,144)	(242)	1,917	9,561
CASH AND CASH EQUIVALENTS AT BEGINNING OF PERIOD	14,124	12,351	11,063	2,548
CASH AND CASH EQUIVALENTS AT END OF PERIOD	12,980	12,109	12,980	12,109
CASH PAYMENTS FOR:
Interest, net of amount capitalized	22	7	188	61
Income taxes	114	7	291	17
SUPPLEMENTAL DISCLOSURE OF NONCASH TRANSACTIONS:
Right-of-use assets acquired under operating leases	53	6	283	692
Flight equipment acquired against supplier credit memo	0	0	512	0
Assets constructed for others	0	35	309	110
Remeasurement of right-of-use asset and lease liability	$ 343	$ 0	$ 343	$ 0