Captain McAllaster was the navigator of a B-26B Invader bomber with the 13th Bomber Squadron, 3rd Bomber Group. On 4 April 1952, while on a night intruder mission, his aircraft crashed near Haeju, North Korea. He was listed as Missing in Action and was presumed dead on 31 March 1954. His remains were not recovered. His name is inscribed on the Courts of the Missing at the Honolulu Memorial.

For his leadership and valor, Captain McAllaster was awarded the Distinguished Flying Cross, the Air Medal with 5 Oak Leaf Clusters, the Purple Heart, the Korean Service Medal, the United Nations Service Medal, the National Defense Service Medal, the Korean Presidential Unit Citation and the Republic of Korea War Service Medal.