Condensed Consolidated Statements of Income - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Nov. 30, 2018	Nov. 30, 2017	Nov. 30, 2018	Nov. 30, 2017
Income Statement [Abstract]
REVENUES	$ 17,824	$ 16,313	$ 34,876	$ 31,610
OPERATING EXPENSES:
Salaries and employee benefits	6,260	5,889	12,520	11,553
Purchased transportation	$ 4,346	$ 3,840	$ 8,313	$ 7,285
Type of cost, good or service [extensible list]	us-gaap:ShippingAndHandlingMember	us-gaap:ShippingAndHandlingMember	us-gaap:ShippingAndHandlingMember	us-gaap:ShippingAndHandlingMember
Rentals and landing fees	$ 836	$ 835	$ 1,659	$ 1,653
Depreciation and amortization	828	756	1,636	1,507
Fuel	1,052	818	2,038	1,521
Maintenance and repairs	751	665	1,486	1,340
Other	2,583	2,395	4,985	4,665
OPERATING EXPENSES	16,656	15,198	32,637	29,524
OPERATING INCOME	1,168	1,115	2,239	2,086
OTHER INCOME (EXPENSE):
Interest, net	(129)	(124)	(241)	(238)
Other retirement plans income	158	147	316	293
Other, net	(20)	1	(36)	(20)
OTHER INCOME (EXPENSE)	9	24	39	35
INCOME BEFORE INCOME TAXES	1,177	1,139	2,278	2,121
PROVISION FOR INCOME TAXES	242	364	508	750
NET INCOME	$ 935	$ 775	$ 1,770	$ 1,371
EARNINGS PER COMMON SHARE:
Basic	$ 3.56	$ 2.89	$ 6.71	$ 5.12
Diluted	3.51	2.84	6.60	5.03
DIVIDENDS DECLARED PER COMMON SHARE	$ 0.65	$ 0.50	$ 1.95	$ 1.50