Allan McCoy’s mother, Winnifred Edith Farquharson (aka Edith Wilhelmina, nicknamed “Winnie”), was born in Lancashire, England in 1900 and came to Toronto with her family before she was 10 years old. Her Scottish father George was a photo engraver for a publishing company. In 1914, the family moved from the Dundas and Sherbourne neighbourhood into a newly built house at 328 Waverley Road.

Allan’s father, Frank Edward McCoy was a butcher who was born in Peterborough, Ontario circa 1902. He married Winnie in July 1921. Allan was born on June 23, 1922 and a brother John Edward followed in 1925. Before Allan started school, the family moved to Chicago, Illinois. In 1928, a sister, Margaret Edith was born. When he was seven, Allan suffered a dangerous bout of pneumonia and recovered slowly. By 1934, Winnie had separated from Frank and had moved back to Toronto with her children into her widowed mother Edith’s house on Waverley.

Allan started at Norway in Grade 7 and in 1936 he entered Grade 9 at Eastern Commerce, learning Stenography. He may have transferred to Danforth Tech but ultimately he went back to Chicago to live with his father and he briefly attended Tilden High, an all-boys technical school. He returned to Toronto in early 1939 and worked for a jeweller on Richmond Street East as a messenger and jewellery polisher. A year later he became a clerk in a jewellery store on Danforth Avenue, west of Woodbine.

Allan's parents had divorced and his mother had married a Mr. Thompson, possibly named Fred. They all eventually lived at 328 Waverley. On February 10, 1941, Allan was in a car accident and cut his chin.

Allan enlisted in the RCAF in August 1941. He stated that he liked to play baseball and that he had taken a 15 minute airplane ride. He hoped to return to his job after the war and wanted to manufacture jewellery. The RCAF tests showed that he had exceptional night vision and he was streamed into the Air Gunner's course. He remained in Toronto until December 1941 and the next month he started the Air Gunner's school at Fingal, near St. Thomas in western Ontario. By the middle of February he was allowed to wear the Air Gunner's badge, although he wasn't yet fully qualified. The next day he was granted leave until March 4, 1942. He was taken out of the RCAF and added to the RAF trainees pool, arriving in Britain on March 24.

Allan's training continued with the RAF in England and then he shifted to advanced air gunnery school in Wales where he achieved 71%. On June 30, he moved to a training group where he trained as night bomber crew on Whitley airplanes. He finally qualified as a fully fledged air gunner on July 6. He continued training until the end of September when he joined No. 10 Conversion Flight. This was a training station where Allan learned how to be crew on the Halifax, a heavy bomber. It was the main aircraft of the RAF's Bomber Command and carried a crew of seven with a pilot, a co-pilot, a navigator, a wireless radio operator, a bomb aimer in the nose, a middle gun turret in the top of the plane with two guns and a tail gunner in the extreme end of the fuselage with four guns. Allan would have trained as a middle gunner or tail gunner.