Allegheny County Airport (IATA: AGC, ICAO: KAGC, FAA LID: AGC) is in West Mifflin, Pennsylvania, 7 miles (11 km) southeast of Pittsburgh. It is the fifth-busiest airport in Pennsylvania following Philadelphia, Pittsburgh, Allentown, and Harrisburg. The airport is owned by the Allegheny County Airport Authority and is the primary FAA designated reliever airport for Pittsburgh International Airport.Allegheny County Airport was dedicated on September 11, 1931. When it was completed, it was third-largest airport in the country, as well as the only hard-surface airport in the country. It was historically the main entrance to metro Pittsburgh via air from its inception until June 1952, when the Greater Pittsburgh Airport (now Pittsburgh International Airport – KPIT) opened for commercial aviatio