Sismey joined the RAAF on 3 February 1941 and was assigned the service number 403605. He received basic training as a pilot in Australia. Under the provisions of the British Commonwealth Air Training Plan (also known as the Empire Air Training Scheme), many Commonwealth aircrews during World War II received advanced training in Canada at Royal Canadian Air Force facilities and, after graduating, were posted to units of their own or other Commonwealth air force units, in various parts of the world. Sismey embarked at Sydney on 13 June 1941 and arrived in Canada on 3 July; he received advanced training at No. 7 Service Flying Training School, RCAF Fort Macleod, near Fort Macleod, Alberta.