On July 9, 1917, Graves enlisted as a cadet in the Royal Flying Corps in Canada to avoid a delay in getting into a US Army's flying program. He was commissioned as a 2nd Lieutenant on October 29, 1917. Later, he was assigned as an instructor in aerial gunnery at the United States Army Air Service training facility at Camp Taliaferro, Hicks Field, Fort Worth, Texas. While station at Hicks Field, he became one of the first pilots to execute elaborate stunts in a Curtiss airplane. In early spring, 1918 he was transferred to the Officers' School of Special Flying at Armour Heights, Toronto, Ontario where he was promoted to 1st Lieutenant in May, 1918. After spending most of his time during the war serving in Canada and stateside, Graves was finally posted overseas and arrived in France on November 5, 1918 just a few days before the signing of the Armistice agreement, which ended the war.