The National Reconnaissance Office (NRO) is one of the 17 U.S. intelligence agencies and considered, along with the Central Intelligence Agency (CIA), National Security Agency (NSA), Defense Intelligence Agency (DIA), and National Geospatial-Intelligence Agency (NGA), to be one of the "big five" U.S. Intelligence agencies. The NRO is headquartered in unincorporated Fairfax County, Virginia, 2 miles (3 km) south of Washington Dulles International Airport.