Condensed Consolidating Financial Statements (Details 3) (USD $) In Millions	3 Months Ended								12 Months Ended
	May 31, 2011	Feb. 28, 2011	Nov. 30, 2010	Aug. 31, 2010	May 31, 2010	Feb. 28, 2010	Nov. 30, 2009	Aug. 31, 2009	May 31, 2011	May 31, 2010	May 31, 2009
Condensed Financial Statements Captions [Line Items]
REVENUES	$ 10,552	$ 9,663	$ 9,632	$ 9,457	$ 9,428	$ 8,701	$ 8,596	$ 8,009	$ 39,304	$ 34,734	$ 35,497
OPERATING EXPENSES:
Salaries and employee benefits									15,276	14,027	13,767
Purchased transportation									5,674	4,728	4,534
Rentals and landing fees									2,462	2,359	2,429
Depreciation and amortization									1,973	1,958	1,975
Fuel									4,151	3,106	3,811
Maintenance and repairs									1,979	1,715	1,898
Impairment and other charges									89	18	1,204
Other									5,322	4,825	5,132
OPERATING EXPENSES									36,926	32,736	34,750
OPERATING INCOME	888	393	469	628	696	416	571	315	2,378	1,998	747
OTHER INCOME (EXPENSE):
Interest, net									(77)	(71)	(59)
Other, net									(36)	(33)	(11)
INCOME BEFORE INCOME TAXES									2,265	1,894	677
PROVISION FOR INCOME TAXES									813	710	579
NET INCOME	558	231	283	380	419	239	345	181	1,452	1,184	98
Parent Company Member
OPERATING EXPENSES:
Salaries and employee benefits									109	91	82
Rentals and landing fees									4	4	4
Depreciation and amortization									1	1	2
Maintenance and repairs									1	1	1
Intercompany charges, net									(222)	(202)	(193)
Other									107	105	104
OTHER INCOME (EXPENSE):
Equity in earnings of subsidiaries									1,452	1,184	98
Interest, net									(88)	(100)	(73)
Intercompany charges, net									104	114	90
Other, net									(16)	(14)	(17)
INCOME BEFORE INCOME TAXES									1,452	1,184	98
NET INCOME									1,452	1,184	98
Guarantor Subsidiaries Member
Condensed Financial Statements Captions [Line Items]
REVENUES									33,124	29,360	29,923
OPERATING EXPENSES:
Salaries and employee benefits									13,206	12,026	11,483
Purchased transportation									4,034	3,424	3,362
Rentals and landing fees									2,209	2,118	2,134
Depreciation and amortization									1,784	1,751	1,706
Fuel									4,003	2,946	3,554
Maintenance and repairs									1,862	1,589	1,755
Impairment and other charges									28		1,098
Intercompany charges, net									(317)	(109)	81
Other									4,392	3,950	4,198
OPERATING EXPENSES									31,201	27,695	29,371
OPERATING INCOME									1,923	1,665	552
OTHER INCOME (EXPENSE):
Equity in earnings of subsidiaries									200	161	103
Interest, net									13	41	28
Intercompany charges, net									(135)	(147)	(118)
Other, net									(14)	(18)	(3)
INCOME BEFORE INCOME TAXES									1,987	1,702	562
PROVISION FOR INCOME TAXES									677	625	514
NET INCOME									1,310	1,077	48
Non Guarantor Subsidiaries Member
Condensed Financial Statements Captions [Line Items]
REVENUES									6,498	5,700	5,851
OPERATING EXPENSES:
Salaries and employee benefits									1,961	1,910	2,202
Purchased transportation									1,745	1,392	1,211
Rentals and landing fees									253	240	296
Depreciation and amortization									188	206	267
Fuel									148	160	257
Maintenance and repairs									116	125	142
Impairment and other charges									61	18	106
Intercompany charges, net									539	311	112
Other									1,032	1,005	1,063
OPERATING EXPENSES									6,043	5,367	5,656
OPERATING INCOME									455	333	195
OTHER INCOME (EXPENSE):
Interest, net									(2)	(12)	(14)
Intercompany charges, net									31	33	28
Other, net									(6)	(1)	9
INCOME BEFORE INCOME TAXES									478	353	218
PROVISION FOR INCOME TAXES									136	85	65
NET INCOME									342	268	153
Consolidation Eliminations Member
Condensed Financial Statements Captions [Line Items]
REVENUES									(318)	(326)	(277)
OPERATING EXPENSES:
Purchased transportation									(105)	(88)	(39)
Rentals and landing fees									(4)	(3)	(5)
Other									(209)	(235)	(233)
OPERATING EXPENSES									(318)	(326)	(277)
OTHER INCOME (EXPENSE):
Equity in earnings of subsidiaries									(1,652)	(1,345)	(201)
INCOME BEFORE INCOME TAXES									(1,652)	(1,345)	(201)
NET INCOME									$ (1,652)	$ (1,345)	$ (201)