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, 2020	May 31, 2019
Property Plant And Equipment [Line Items]
Net Book Value at May 31,	$ 33,608	$ 30,429
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,	$ 13,448	11,975
Narrow-body and Feeder Aircraft and Related Equipment [Member]
Property Plant And Equipment [Line Items]
Depreciable lives range	5 to 18 years
Net Book Value at May 31,	$ 2,478	2,696
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,	$ 4,499	4,157
Information Technology [Member]
Property Plant And Equipment [Line Items]
Depreciable lives range	2 to 10 years
Net Book Value at May 31,	$ 1,795	1,553
Vehicles And Trailers [Member]
Property Plant And Equipment [Line Items]
Depreciable lives range	3 to 15 years
Net Book Value at May 31,	$ 4,345	4,042
Facilities and Other Property [Member]
Property Plant And Equipment [Line Items]
Depreciable lives range	2 to 40 years
Net Book Value at May 31,	$ 7,043	$ 6,006