Condensed Consolidating Financial Statements (Details 3) (USD $) In Millions	3 Months Ended
	Aug. 31, 2011	Aug. 31, 2010
Condensed Financial Statements Captions [Line Items]
REVENUES	$ 10,521	$ 9,457
OPERATING EXPENSES:
Salaries and employee benefits	4,004	3,803
Purchased transportation	1,518	1,327
Rentals and landing fees	620	601
Depreciation and amortization	509	479
Fuel	1,244	887
Maintenance and repairs	551	517
Other	1,338	1,215
OPERATING EXPENSES	9,784	8,829
OPERATING INCOME	737	628
OTHER INCOME (EXPENSE):
Interest, net	(11)	(18)
Other, net	(2)	(7)
INCOME BEFORE INCOME TAXES	724	603
PROVISION FOR INCOME TAXES	260	223
NET INCOME	464	380
Parent Company Member
OPERATING EXPENSES:
Salaries and employee benefits	33	38
Rentals and landing fees	1	1
Intercompany charges, net	(58)	(71)
Other	24	32
OTHER INCOME (EXPENSE):
Equity in earnings of subsidiaries	464	380
Interest, net	(20)	(24)
Intercompany charges, net	21	27
Other, net	(1)	(3)
INCOME BEFORE INCOME TAXES	464	380
NET INCOME	464	380
Guarantor Subsidiaries Member
Condensed Financial Statements Captions [Line Items]
REVENUES	9,007	7,893
OPERATING EXPENSES:
Salaries and employee benefits	3,531	3,249
Purchased transportation	1,080	920
Rentals and landing fees	555	537
Depreciation and amortization	471	432
Fuel	1,224	841
Maintenance and repairs	528	483
Intercompany charges, net	(90)	(92)
Other	1,125	986
OPERATING EXPENSES	8,424	7,356
OPERATING INCOME	583	537
OTHER INCOME (EXPENSE):
Equity in earnings of subsidiaries	71	26
Interest, net	8	8
Intercompany charges, net	(28)	(35)
Other, net	(2)	(4)
INCOME BEFORE INCOME TAXES	632	532
PROVISION FOR INCOME TAXES	215	196
NET INCOME	417	336
Non Guarantor Subsidiaries Member
Condensed Financial Statements Captions [Line Items]
REVENUES	1,584	1,646
OPERATING EXPENSES:
Salaries and employee benefits	440	516
Purchased transportation	464	432
Rentals and landing fees	65	64
Depreciation and amortization	38	47
Fuel	20	46
Maintenance and repairs	23	34
Intercompany charges, net	148	163
Other	232	253
OPERATING EXPENSES	1,430	1,555
OPERATING INCOME	154	91
OTHER INCOME (EXPENSE):
Interest, net	1	(2)
Intercompany charges, net	7	8
Other, net	1
INCOME BEFORE INCOME TAXES	163	97
PROVISION FOR INCOME TAXES	45	27
NET INCOME	118	70
Consolidation Eliminations Member
Condensed Financial Statements Captions [Line Items]
REVENUES	(70)	(82)
OPERATING EXPENSES:
Purchased transportation	(26)	(25)
Rentals and landing fees	(1)	(1)
Other	(43)	(56)
OPERATING EXPENSES	(70)	(82)
OTHER INCOME (EXPENSE):
Equity in earnings of subsidiaries	(535)	(406)
INCOME BEFORE INCOME TAXES	(535)	(406)
NET INCOME	$ (535)	$ (406)