As of early 2026, United Airlines holds the title for the largest mainline fleet in the world, operating approximately 1,037 aircraft. United surged ahead of its competitors by following an aggressive "United Next" growth strategy, which involved taking delivery of hundreds of new Boeing 737 MAX and Airbus A321neo jets to expand its global network. American Airlines follows closely behind in second place with a fleet of roughly 992 aircraft, while Delta Air Lines is a very narrow third with about 989 planes. While United leads in total numbers, American is often cited as having the "youngest" fleet among the "Big Three" U.S. carriers due to its earlier retirement of aging models. It is important to distinguish between "Mainline" fleets and "Group" fleets; when including regional subsidiaries (like American Eagle or United Express), the total aircraft under one brand's control can exceed 1,500. Outside of the United States, China Southern Airlines is the largest carrier in Asia, but it still remains smaller in total hull count than the major U.S. giants.