Condensed Consolidated Statement of Cash Flows (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
CASH FLOWS FROM OPERATING ACTIVITIES [Abstract]
Net Income	$ 178	$ 459	$ 99
Adjustments to reconcile net income (loss) to cash provided by operating activities [Abstract]
Depreciation and amortization	715	628	616
(Gain) loss recognized in income on derivatives	(90)	(139)	(14)
Deferred Income Taxes and Tax Credits	123	133	72
Amortization of deferred gains on sale and leaseback of aircraft	(13)	(14)	(12)
Changes in certain assets and liabilities [Abstract]
Increase (Decrease) in Accounts and Other Receivables	(26)	(26)	40
Increase (Decrease) in Other Current Assets	(196)	(8)	(27)
Accounts payable and accrued liabilities	253	193	59
Air traffic liability	262	153	81
Cash collateral received from (provided to) derivative counterparties	(195)	265	(90)
Other, net	194	(361)	133
Net cash provided by (used in) operating activities	1,385	1,561	985
CASH FLOWS FROM INVESTING ACTIVITIES [Abstract]
Payments to acquire business, net of cash acquired	(35)	0	0
Purchases of property and equipment, net	(968)	(493)	(585)
Purchases of short-term investments	(5,362)	(5,624)	(6,106)
Proceeds from sales of short-term investments	5,314	4,852	5,120
Other, net	0	0	2
Net cash provided by (used in) investing activities	(1,051)	(1,265)	(1,569)
CASH FLOWS FROM FINANCING ACTIVITIES [Abstract]
Proceeds from issuance of long-term debt	0	0	455
Proceeds from credit line borrowing	0	0	83
Proceeds from sale leaseback transactions	0	0	381
Proceeds from Employee stock plans	39	55	20
Proceeds from termination of interest rate derivatives	76	0	0
Proceeds from Convertible Debt			0
Payments of long-term debt and capital lease obligations	(557)	(155)	(86)
Payments of Convertible Debt	(81)	0
Payment of revolving credit facility	0	0	(400)
Payment of credit line borrowing	0	(44)	(97)
Payments of cash dividends	(14)	(13)	(13)
Repurchase of common stock	(225)	0	0
Other, net	(4)	8	(13)
Net cash provided by (used in) financing activities	(766)	(149)	330
NET CHANGE IN CASH AND CASH EQUIVALENTS	(432)	147	(254)
CASH AND CASH EQUIVALENTS AT BEGINNING OF PERIOD	1,261	1,114	1,368
CASH AND CASH EQUIVALENTS AT END OF PERIOD	829	1,261	1,114
CASH PAYMENTS FOR [Abstract]
Interest, net of amount capitalized	185	135	152
Income taxes	13	274	5
Supplemental Cash Flow Disclosures [Abstract]
Fair Value of common stock issued in connection with the business acquisition	523	0	0
Debt Conversion, Converted Instrument, Amount	$ 78	$ 0	$ 0