Hooper enlisted in the
Royal Engineers on 1 November 1915. He transferred to the
Royal Flying Corps in August 1916. He joined
No. 11 Squadron RFC as pilot of a
Bristol F.2 Fighter on 12 April 1917, three days before his 26th birthday. He scored his first victory on 26 June 1917. On 1 July 1917, Hooper was promoted to lieutenant. Eight days later, on 9 July 1917, he was raised to
flight commander and temporary captain. He scored twice more while with 11 Squadron, the last on 11 September 1917, with
Leslie Powell in the gunner's pit. Hooper then collected a
Military Cross and transferred to
No. 38 Squadron RFC on training duty for a rest. He returned to combat with
No. 20 Squadron RAF, and took up his winning ways there on 24 September 1918. With
Harold Leslie Edwards manning the guns, he scored triple wins on 25 and 29 September, to become a double ace. On 10 November, he racked up his final victory, reaching six German fighters destroyed and five driven down out of control. He had also participated in many bombing raids, by both day and night. ==Post-war==