Since opening on Feb. 28, 1995, Denver International Airport (DEN) has become the nation's fifth-busiest airport in the United States and 17th-busiest in the world. With more than 53 million passengers in 2014, DEN is one of the busiest hubs in the worldÍs largest aviation market, the United States, and is ColoradoÍs primary economic engine, generating more than $26 billion in annual economic impact for the state (Colorado Department of Transportation, 2013). DEN is one of the few major U.S. airports with room to expand its current facilities to accommodate future growth. Encompassing 53 square miles (137.8 square kilometers) of land, DEN is twice the size of Manhattan Island, and is larger than the city boundaries of Boston, Miami, or San Francisco. DEN is the largest airport site in North America and the second-largest in the world. The efficient layout of six non-intersecting runways allows for multiple simultaneous aircraft movements.