Washington Dulles International Airport (IATA: IAD) is an international airport in Loudoun and Fairfax counties in Virginia, 26 miles (42 km) west of downtown Washington, D.C. The airport serves the Baltimore–Washington Metropolitan Area, centered on the District of Columbia. The airport is named after John Foster Dulles, the 52nd Secretary of State who served under President Dwight D. Eisenhower. The Dulles main terminal is a well-known landmark designed by Eero Saarinen. Operated by the Metropolitan Washington Airports Authority, Dulles Airport occupies 11,830 acres (47.9 km2) straddling the Loudoun-Fairfax line. Most of the airport is in the unincorporated community of Dulles, in Loudoun County, with a small portion in the unincorporated community of Chantilly in Fairfax County.
Dulles is the busiest airport in the Washington metropolitan area, and second busiest airport in the larger Baltimore–Washington metropolitan area (after BWI Airport) with over 21 million passengers a year. With nearly all of the international passenger traffic in the Baltimore-Washington region, Dulles is the busiest international airport in the Mid-Atlantic outside the New York metropolitan area. On a typical day, more than 60,000 passengers pass through Washington Dulles to and from more than 125 destinations around the world. Dulles is a hub for United Airlines and an East Coast focus city for Frontier Airlines that will be deprecated on October 24, 2015. Wikipedia