Condensed Consolidated Statements of Income - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Nov. 30, 2017	Nov. 30, 2016	Nov. 30, 2017	Nov. 30, 2016
Income Statement [Abstract]
REVENUES	$ 16,313	$ 14,931	$ 31,610	$ 29,594
OPERATING EXPENSES:
Salaries and employee benefits	5,742	5,353	11,260	10,664
Purchased transportation	3,840	3,431	7,285	6,671
Rentals and landing fees	835	802	1,653	1,592
Depreciation and amortization	756	740	1,507	1,479
Fuel	818	658	1,521	1,308
Maintenance and repairs	665	579	1,340	1,177
Other	2,395	2,201	4,665	4,272
OPERATING EXPENSES	15,051	13,764	29,231	27,163
OPERATING INCOME	1,262	1,167	2,379	2,431
OTHER INCOME (EXPENSE):
Interest, net	(124)	(119)	(238)	(232)
Other, net	1	30	(20)	21
OTHER INCOME (EXPENSE)	(123)	(89)	(258)	(211)
INCOME BEFORE INCOME TAXES	1,139	1,078	2,121	2,220
PROVISION FOR INCOME TAXES	364	378	750	805
NET INCOME	$ 775	$ 700	$ 1,371	$ 1,415
EARNINGS PER COMMON SHARE:
Basic	$ 2.89	$ 2.63	$ 5.12	$ 5.32
Diluted	2.84	2.59	5.03	5.24
DIVIDENDS DECLARED PER COMMON SHARE	$ 0.50	$ 0.40	$ 1.50	$ 1.20