Condensed Consolidated Statements of Income - USD ($) $ in Millions	3 Months Ended
	Aug. 31, 2017	Aug. 31, 2016
Income Statement [Abstract]
REVENUES	$ 15,297	$ 14,663
OPERATING EXPENSES:
Salaries and employee benefits	5,518	5,311
Purchased transportation	3,445	3,240
Rentals and landing fees	818	790
Depreciation and amortization	751	739
Fuel	703	650
Maintenance and repairs	675	598
Other	2,270	2,071
OPERATING EXPENSES	14,180	13,399
OPERATING INCOME	1,117	1,264
OTHER INCOME (EXPENSE):
Interest, net	(114)	(113)
Other, net	(21)	(9)
OTHER INCOME (EXPENSE)	(135)	(122)
INCOME BEFORE INCOME TAXES	982	1,142
PROVISION FOR INCOME TAXES	386	427
NET INCOME	$ 596	$ 715
EARNINGS PER COMMON SHARE:
Basic	$ 2.22	$ 2.69
Diluted	2.19	2.65
DIVIDENDS DECLARED PER COMMON SHARE	$ 1.00	$ 0.80