400 "City of Toronto" Tactical Helicopter and Training Squadron is part of 1 Wing, and as such a lodger unit of Canadian Forces Base Borden.

10 Army Co-Operation Squadron at Toronto, Ontario on 5 October 1932, when it flew from the Trethewey Farm Airfield (De Lesseps Field) from 1934 to 1939.

When the squadron was called out on active service 3 September 1939, it first deployed to CFB Rockcliffe (now Ottawa/Rockcliffe Airport), Ottawa, Ontario for conversion to the Westland Lysander aircraft.

During the war, it flew the Westland Lysander, Curtiss Tomahawk, North American Mustang, de Havilland Mosquito and Supermarine Spitfire primarily in the armed and unarmed reconnaissance role.

At the end of the war, 400 Squadron was disbanded on 7 August 1945, at the captured Lüneburg Airfield (Advanced Landing Ground B156) in western Germany.

400 "City of Toronto" (Fighter) Squadron, as part of 2 Air Reserve Wing, first flew Beechcraft Expeditor starting in 1958 and then the DHC Otter in 1960.