NOTE: Airports are included if they serve at least 0.05% of all enplaned (boarded) passengers in the United States. They are categorized based on their share of total enplaned passengers: Large, 1% or more; Medium, 0.25%–0.99%; and Small, 0.05%–0.24%.

SOURCE: U.S. Department of Transportation, Bureau of Transportation Statistics, Office of Airline Information, T-100 Domestic Market database, as of November 2013.