Richmond, approximately 30 kilometres north-west of Sydney, was the second permanent base established for the Royal Australian Air Force (RAAF) and today is its largest. Land in the Richmond area known as Ham Common was first used for an airfield in 1912. In 1914 a civilian flying school was established there and in 1916 the New South Wales government opened a flying school to prepare civilian pilots for service with the either the Australian or Royal Flying Corps; it remained in operation until 1919. The Department of Defence acquired the site for the fledgling RAAF in 1923 and the first squadrons arrived in 1925. In subsequent years Richmond has been home to a wide range of RAAF base establishments and squadrons. The base was expanded during the 1930s, during the Second World War, and in the 1960s and is today home to the squadrons of the RAAF's Air Transport Command.