This was the first Canadian squadron formed overseas that had no ties to any previous flying unit.
Created on 1 March 1941 as No. 403 Army Cooperation (AC) Squadron equipped with the Curtiss Tomahawk.
In May of 1941 the Squadron’s role was changed to Fighter and it exchanged its Tomahawks for Supermarine Spitfire Mk Is and moved from Baginton to Ternhill.
The Squadron moved again in August to Hornchurch to commence offensive operations and replaced its Mk I’s with new Spitfire Mk Vb’s.
The Squadron continued operations from various airfields in the south of England until July 1942, when it withdrew to Catterick. It returned briefly to Manston to participate in operations over Dieppe on the 19th of August.
The Squadron then moved to Kenley in January 1943 and converted to Spitfire Mk IX’s. Kenley became No. 127 Airfield in No. 17 Fighter Wing, and then 127 Wing of the new 2nd TAF (Tactical Air Force) later in the year.
In April 1944 the wing moved to Tangmere for operations during the Normandy invasion, moving to French soil on 16 June. Patrols over the front and frequent aerial engagements followed throughout the summer and fall. Moving into Belgium in November the Squadron maintained regular contact with the remainder of the Luftwaffe and this ensured that the unit ended hostilities as the RCAF’s second highest scoring unit with 125 1/4 victories claimed.
The code letters carried by the Squadron during this period were KH.
The Squadron was disbanded at Fassberg, Germany on 10 July 1945.