Condensed Consolidated Statement of Cash Flows - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income (loss)	$ (915)	$ 741	$ (1,009)	$ 1,128
Adjustments to reconcile net income to cash provided by (used in) operating activities:
Depreciation and amortization	313	302	624	598
Unrealized/realized (gain) loss on fuel derivative instruments	6	0	8	0
Deferred income taxes	(181)	36	(230)	50
Gain on sale-leaseback transactions	(222)	0	(222)	0
Changes in certain assets and liabilities:
Accounts and other receivables	(119)	18	64	(204)
Other assets	224	86	282	115
Accounts payable and accrued liabilities	1,200	(89)	(90)	(346)
Air traffic liability	667	(30)	1,368	914
Other liabilities	(74)	(54)	(206)	(123)
Cash collateral received from (provided to) derivative counterparties	12	(15)	7	0
Other, net	(14)	(29)	(76)	(61)
Net cash provided by operating activities	897	966	520	2,071
CASH FLOWS FROM INVESTING ACTIVITIES:
Capital expenditures	(113)	(230)	(336)	(390)
Supplier Proceeds	128	0	428	0
Purchases of short-term investments	(1,316)	(550)	(2,345)	(800)
Proceeds from sales of short-term and other investments	818	528	1,765	1,103
Net cash provided by (used in) investing activities	332	(252)	327	(87)
CASH FLOWS FROM FINANCING ACTIVITIES:
Issuance of common stock	2,294	0	2,294	0
Proceeds from issuance of long-term debt	3,997	0	4,497	0
Proceeds from term loan credit facility	2,683	0	3,683	0
Proceeds from revolving credit facility	0	0	1,000	0
Proceeds from convertible notes	2,300	0	2,300	0
Proceeds from Payroll Support Program loan and warrants	885	0	885	0
Proceeds from Employee stock plans	13	10	24	20
Repurchase of common stock	0	(450)	(451)	(950)
Payments of long-term debt and finance lease obligations	(159)	(75)	(237)	(175)
Payments of cash dividends	0	(98)	(188)	(276)
Capitalized financing costs	171	0	176	0
Other, net	23	1	8	(11)
Net cash provided by (used in) financing activities	7,182	(612)	8,956	(1,392)
NET CHANGE IN CASH AND CASH EQUIVALENTS	8,411	102	9,803	592
CASH AND CASH EQUIVALENTS AT BEGINNING OF PERIOD	3,940	2,344	2,548	1,854
CASH AND CASH EQUIVALENTS AT END OF PERIOD	12,351	2,446	12,351	2,446
CASH PAYMENTS FOR:
Interest, net of amount capitalized	40	33	54	48
Income taxes	5	314	10	318
Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract]
Right-of-use assets acquired under operating leases	661	0	686	0
Assets Constructed for Others	41	24	75	45
Sale Leaseback Cash Proceeds Investing	815	0	815	0
364-Day Term Loan Credit Facility
Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract]
Repayment of Short-term Debt	(3,683)	0	(3,683)	0
Revolving Credit Facility
CASH FLOWS FROM FINANCING ACTIVITIES:
Payments of revolving credit facility	$ (1,000)	$ 0	$ (1,000)	$ 0