Washington Dulles International Airport (IAD) is located in Chantilly, Virginia, on 12,000 acres of land in the suburbs of downtown Washington, DC. The Main Terminal opened in 1962 and was designed by architect Eero Saarinen. Dulles is a major hub for domestic and international air travel with a mixture of legacy and low fare carriers that provide air service throughout the world. Flights operate from midfield concourses A, B, C and D and from Z-gates connected to the Main Terminal. The Airport has invested in its infrastructure through a major capital program, which included two parking garages, a new airport traffic control tower, expanded B-gates, a new fourth runway, an AeroTrain people mover system and an expanded International Arrivals Building. The airport is connected to the region’s highway system via an Authority-operated, 16-mile Airport Access Highway dedicated to airport users. A 23-mile expansion of the region's Metrorail system that includes a station at Dulles is under construction.