Patuxent River Naval Air Station, also known as Trapnell Field (IATA: NHK, ICAO: KNHK), is a major U.S. Navy installation located in St. Mary's County, Maryland, along the Patuxent River where it meets the Chesapeake Bay. It serves as the home of the Naval Air Systems Command (NAVAIR) and is the Navy's primary site for aircraft research, development, test, and evaluation. The station hosts the U.S. Naval Test Pilot School, which has trained generations of military test pilots and flight officers. The airfield is named after Rear Admiral Frank Trapnell, a distinguished naval aviator and test pilot. While primarily a military facility, the field also supports limited general aviation operations. As a restricted military installation, Patuxent River NAS does not offer commercial airline service. Its operations are focused on cutting-edge aviation testing, including fixed-wing aircraft, helicopters, and unmanned aerial systems for the U.S. Navy and Marine Corps.