The Muir Army Airfield (IATA: MUI, ICAO: KMUI, FAA LID: MUI) is a military airport at Fort Indiantown Gap, near Annville, Pennsylvania, United States. It is home to the 28th Combat Aviation Brigade and Eastern Army National Guard Aviation Training Site (EAATS), operated by the Pennsylvania Army National Guard. It is 24 nautical miles (44 kilometres) northeast of the central business district of Harrisburg, in South Central Pennsylvania. The airfield has one active runway designated 7/25 with a 3,978 ft × 98 ft (1,212 m × 30 m) asphalt surface.