When measuring by the total number of individual passengers carried annually, American Airlines consistently holds the top spot globally. As of the most recent 2025-2026 data cycles, American Airlines leverages its massive domestic network in the United States and its extensive international "oneworld" alliance connections to transport over 200 million passengers per year. However, the answer can shift depending on the metric used. If you measure by "Scheduled Passenger-Kilometers Flown" (RPKs), which factors in the distance traveled, the ranking often fluctuates between American, Delta, and United. In the low-cost carrier sector, Southwest Airlines leads in domestic volume within the U.S., while Ryanair dominates the European market, often carrying more international passengers than any other single airline in the world. The sheer scale of American Airlines' fleet, which exceeds 900 aircraft, allows it to maintain the highest overall passenger throughput by sheer frequency of flights across its numerous global hubs like Dallas/Fort Worth and Charlotte.