Description of Business Segments and Summary of Significant Accounting Policies - Schedule of Depreciable Lives and Net Book Value of Our Property and Equipment (Details) - USD ($) $ in Millions	12 Months Ended
	May 31, 2021	May 31, 2020
Property Plant And Equipment [Line Items]
Net Book Value at May 31,	$ 35,752	$ 33,608
Wide-body Aircraft and Related Equipment [Member]
Property Plant And Equipment [Line Items]
Depreciable lives range	15 to 30 years
Net Book Value at May 31,	$ 14,812	13,448
Narrow-body and Feeder Aircraft and Related Equipment [Member]
Property Plant And Equipment [Line Items]
Depreciable lives range	5 to 30 years
Net Book Value at May 31,	$ 2,307	2,478
Package Handling and Ground Support Equipment [Member]
Property Plant And Equipment [Line Items]
Depreciable lives range	3 to 30 years
Net Book Value at May 31,	$ 5,269	4,499
Information Technology [Member]
Property Plant And Equipment [Line Items]
Depreciable lives range	2 to 10 years
Net Book Value at May 31,	$ 1,863	1,795
Vehicles And Trailers [Member]
Property Plant And Equipment [Line Items]
Depreciable lives range	3 to 15 years
Net Book Value at May 31,	$ 4,033	4,345
Facilities and Other Property [Member]
Property Plant And Equipment [Line Items]
Depreciable lives range	2 to 40 years
Net Book Value at May 31,	$ 7,468	$ 7,043