Authorized as No. 18 (Bomber) Squadron (Auxiliary) at Montreal, Quebec on 1 September 1934, the unit commenced flying training in May 1936 when it received four Moth aircraft. It was renumbered No. 118 Squadron on 15 November 1937. Called out on voluntary full-time duty on 3 September 1939, the unit was redesignated Coast Artillery Co-operation on 28 October and ordered to Saint John, New Brunswick; there it was equipped with Atlas and Lysander aircraft. Redesignated Fighter on 8 August 1940, but not converted, the squadron was disbanded on 27 September 1940.
Authorized on 8 August 1940,1 the squadron was reformed as a Fighter unit at Rockcliffe (Ottawa), Ontario, beginning with "A" Flight on 13 December 1940, and completed on 13 January 1941. Equipped with Grumman Goblin aircraft, it moved to Dartmouth, Nova Scotia in July, being the only fighter unit then available for East Coast defence. In November 1941 it was re-equipped with Kittyhawk aircraft, and in June 1942 was transferred to Annette Island, Alaska as part of the RCAF reinforcement to the United States Army Air Forces. The pilots made the 4000-mile trip by air - the first fighter unit to fly from coast to coast. Selected as one of six home fighter squadrons for overseas duty in October 1943, the unit was redesignated No. 438 (Fighter Bomber) Squadron at Digby, Lincolnshire, England on 18 November 1943.
First Mission: 11 November 1939, Atlas 404 from Saint John with F/L McKay and crew - reconnaissance of north shore of the Bay of Fundy to investigate a reported submarine; aircraft returned after 15 minutes because of engine trouble (faulty plugs) and adverse weather.
Last Mission: 27 April 1940, Lysander 423 from Saint John with F/0 J.W. St. Pierre - 30-minute reconnaissance of the Bay of Fundy.
First Mission: 22 July 1941, 4 Goblins from Dartmouth - uneventful scramble.
Last Mission: 29 September 1943, 2 Kittyhawks from Sea Island - dawn patrol.
Sorties: 18
Operational/Non-operational Flying Hours: 21/1002.
Victories: nil.
Casualties: nil.
Sorties: 251
Operational/Non-operational Flying Hours: 267/8332.
Victories: nil; attacked U-boat with mnachine-gun fire.
Casualties: Operational: nil. Non-operational: 5 aircraft; 5 pilots killed or missing.
Honours and Awards nil.