The largest airline in the world can be measured in several ways. , United Airlines was the largest in terms of available seat miles (ASM), revenue seat miles (RPM), mainline fleet size, the number of both mainline employees and destinations served; Delta Air Lines was the most valuable by revenue, assets, market capitalization, and brand value; American Airlines Group carries the most passengers and has the most employees when American Eagle is included; FedEx Express carries the most freight in tonne-kilometers; Southwest Airlines has the greatest number of routes; and Turkish Airlines serves the most countries.
Note that Emirates is a state-owned company, and is thus not included in this list of public companies. Its 2024 revenue was estimated to be around $37.4B or 5th place. Qatar Airways Group is similarly privately held with its 2024 revenue of around $22.2B or 10th place (with Emirates included).
Numbers are listed in billions of available seat miles.
Numbers are listed in billions of ASKs.