The United States of America is being the top country by air transport freight in the world. As of 2015, air transport freight in the United States of America was 37,219 million ton-km that accounts for 19.80 % of the world's air transport freight. The top 5 countries (others are China, the United Arab Emirates, Republic of Korea, and Hong Kong) account for 51.20 % of it. The world's total air transport freight was estimated at 188,000 million ton-km in 2015.
Air freight is the volume of freight, express, and diplomatic bags carried on each flight stage (operation of an aircraft from takeoff to its next landing), measured in metric tons times kilometers traveled.