727 Million Seats This Summer: These Are The Biggest US Airlines In 2025

OAG has released the latest data on the largest airlines in the US by seat numbers. Unsurprisingly, the list is headed by the four major US carriers: United Airlines, Delta Air Lines, American Airlines, and Southwest Airlines. These have 74% of US capacity, claiming 538 million of 727 million seats. These airlines also have the world’s largest fleets of aircraft, and, over the years, they have consolidated their position as the US’ leading carriers through a series of mergers.