Condensed Consolidated Statements of Income - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Nov. 30, 2019	Nov. 30, 2018	Nov. 30, 2019	Nov. 30, 2018
Income Statement [Abstract]
REVENUES	$ 17,324	$ 17,824	$ 34,372	$ 34,876
OPERATING EXPENSES:
Salaries and employee benefits	6,235	6,260	12,322	12,520
Purchased transportation	4,328	4,346	8,356	8,313
Rentals and landing fees	924	836	1,844	1,659
Depreciation and amortization	901	828	1,780	1,636
Fuel	890	1,052	1,760	2,038
Maintenance and repairs	774	751	1,542	1,486
Asset impairment charges	66		66
Other	2,652	2,583	5,171	4,985
OPERATING EXPENSES	16,770	16,656	32,841	32,637
OPERATING INCOME	554	1,168	1,531	2,239
OTHER INCOME (EXPENSE):
Interest, net	(151)	(131)	(288)	(258)
Other retirement plans income	168	158	336	316
Other, net	1	(18)	(11)	(19)
OTHER INCOME (EXPENSE)	18	9	37	39
INCOME BEFORE INCOME TAXES	572	1,177	1,568	2,278
PROVISION FOR INCOME TAXES	12	242	263	508
NET INCOME	$ 560	$ 935	$ 1,305	$ 1,770
EARNINGS PER COMMON SHARE:
Basic	$ 2.15	$ 3.56	$ 5.00	$ 6.71
Diluted	2.13	3.51	4.97	6.60
DIVIDENDS DECLARED PER COMMON SHARE	$ 0.65	$ 0.65	$ 1.95	$ 1.95