Denver International Airport (DIA) is located in Denver, Colorado, United States. The airport has two terminals, the A and B concourses, and three runways. The airport serves as a major international gateway for air travel into Colorado and the United States, with more than 36 million passengers in 2017. It also serves as a regional hub for American Airlines, Delta Air Lines, United Airlines, and Southwest Airlines. DIA is the 24th busiest airport in the world by passenger traffic and the 15th busiest airport in the United States. In addition to airline services, DIA is home to Colorado Convention Center and the University of Denver's Anschutz Medical Campus.