Condensed Consolidated Statement of Cash Flows - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income (loss)	$ (1,157)	$ 659	$ (2,166)	$ 1,787
Adjustments to reconcile net income to cash provided by (used in) operating activities:
Depreciation and amortization	315	308	940	906
Unrealized/realized loss on fuel derivative instruments	17	0	25	0
Deferred income taxes	(298)	174	(528)	224
Gain on sale-leaseback transactions	0	0	(222)	0
Changes in certain assets and liabilities:
Accounts and other receivables	(123)	(88)	(60)	(292)
Other assets	84	79	366	195
Accounts payable and accrued liabilities	26	106	(65)	(240)
Air traffic liability	216	(17)	1,584	897
Other liabilities	(106)	(87)	(312)	(210)
Cash collateral received from (provided to) derivative counterparties	(5)	0	2	0
Other, net	(19)	(43)	(95)	(104)
Net cash provided by (used in) operating activities	(1,050)	1,091	(531)	3,163
CASH FLOWS FROM INVESTING ACTIVITIES:
Capital expenditures	(89)	(375)	(425)	(766)
Supplier Proceeds	0	0	428	0
Proceeds from sale-leaseback transactions	0	0	815	0
Purchases of short-term investments	(1,536)	(529)	(3,881)	(1,329)
Proceeds from sales of short-term and other investments	1,191	545	2,956	1,648
Net cash used in investing activities	(434)	(359)	(107)	(447)
CASH FLOWS FROM FINANCING ACTIVITIES:
Issuance of common stock	0	0	2,294	0
Proceeds from issuance of long-term debt	1,125	0	5,622	0
Proceeds from term loan credit facility	0	0	3,683	0
Proceeds from revolving credit facility	0	0	1,000	0
Proceeds from convertible notes	0	0	2,300	0
Proceeds from Payroll Support Program loan and warrants	130	0	1,016	0
Proceeds from Employee stock plans	13	9	36	29
Repurchase of common stock	0	(500)	(451)	(1,450)
Payments of long-term debt and finance lease obligations	(59)	(70)	(295)	(245)
Payments of cash dividends	0	(96)	(188)	(372)
Payments of terminated interest rate derivative instruments	(31)	0	(31)	0
Capitalized Financing Items	44	0	(133)	0
Other, net	20	(33)	29	(44)
Net cash provided by (used in) financing activities	1,242	(690)	10,199	(2,082)
NET CHANGE IN CASH AND CASH EQUIVALENTS	(242)	42	9,561	634
CASH AND CASH EQUIVALENTS AT BEGINNING OF PERIOD	12,351	2,446	2,548	1,854
CASH AND CASH EQUIVALENTS AT END OF PERIOD	12,109	2,488	12,109	2,488
CASH PAYMENTS FOR:
Interest, net of amount capitalized	7	11	61	59
Income taxes	7	169	17	487
Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract]
Right-of-use assets acquired under operating leases	6	0	692	0
Assets Constructed for Others	35	28	110	73
364-Day Term Loan Credit Facility
Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract]
Repayment of Short-term Debt	0	0	(3,683)	0
Revolving Credit Facility
CASH FLOWS FROM FINANCING ACTIVITIES:
Payments of revolving credit facility	$ 0	$ 0	$ (1,000)	$ 0