Condensed Consolidated Statement of Cash Flows - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 615	$ 528	$ 1,811	$ 1,610
Adjustments to reconcile net income to cash provided by (used in) operating activities:
Depreciation and amortization	301	302	870	939
Aircraft grounding charge	0	63	0	63
Unrealized/realized (gain) loss on fuel derivative instruments	(2)	(42)	(13)	(20)
Deferred income taxes	104	98	308	219
Changes in certain assets and liabilities:
Accounts and other receivables	(13)	0	(109)	(23)
Other assets	(30)	(64)	(243)	(264)
Accounts payable and accrued liabilities	161	87	80	(157)
Air traffic liability	52	(119)	1,018	802
Cash collateral received from derivative counterparties	10	151	150	286
Other, net	73	(8)	32	(89)
Net cash provided by operating activities	1,271	996	3,904	3,366
CASH FLOWS FROM INVESTING ACTIVITIES:
Capital expenditures	(454)	(638)	(1,384)	(1,603)
Assets constructed for others	(8)	(17)	(49)	(113)
Purchases of short-term investments	(678)	(531)	(1,607)	(1,653)
Proceeds from sales of short-term and other investments	531	566	1,665	1,696
Payments for (Proceeds from) Other Investing Activities	5	0	5	0
Net cash used in investing activities	(604)	(620)	(1,370)	(1,673)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from Employee stock plans	9	7	26	22
Reimbursement for assets constructed for others	8	17	165	113
Payments of long-term debt and capital lease obligations	(98)	(106)	(255)	(534)
Payments of cash dividends	(91)	(75)	(332)	(274)
Repayment of construction obligation	(8)	(2)	(22)	(7)
Repurchase of common stock	(500)	(300)	(1,500)	(1,250)
Other, net	3	6	(7)	17
Net cash used in financing activities	(677)	(453)	(1,925)	(1,913)
NET CHANGE IN CASH AND CASH EQUIVALENTS	(10)	(77)	609	(220)
CASH AND CASH EQUIVALENTS AT BEGINNING OF PERIOD	2,114	1,537	1,495	1,680
CASH AND CASH EQUIVALENTS AT END OF PERIOD	2,104	1,460	2,104	1,460
CASH PAYMENTS FOR:
Interest, net of amount capitalized	18	16	70	61
Income taxes	38	229	212	611
SUPPLEMENTAL DISCLOSURE OF NONCASH TRANSACTIONS
Flight equipment under capital leases	18	77	32	180
Assets constructed for others	$ 46	$ 39	$ 126	$ 127