In 1941, Keith trained as a pilot via the British Commonwealth Air Training Plan. He graduated from the Initial Training School in late January 1941, and then attended the Elementary Flying Training School in March. He graduated from Service Flying Training School in June 1941 and was posted overseas, joining No. 402 "City of Winnipeg" Squadron RCAF where he flew the Hurricane IIB, until changing to Spitfire VBs during the Dieppe Raid in August 1942.