Opened in Mar 1915, Northolt was one of the earliest military airfields in England, intended for night defence against Zeppelin raids. Drainage was improved and Type A hangars were built during the 1920s. The RAFs first Hurricanes arrived in Jan 1938. It was extended during 1944 to support large transport aircraft and between 1946 and 1954 it served as Londons main civilian airport, until Heathrow was opened.
Once returned to the RAF, the civilian building on the south side were demolished and eventually replaced. The Metropolitan Communciations Squadron moved in during 1957 and this has continued to be a principal role of the base ever since. As well as visiting military VIPS and occasional Heads of State, the base has also been used for discrete arrivals and departures for Government purposes. It is also the home of 1 AIDU, the authority for distributing RAF flight planning and air safety material.