Stevens joined the Royal Flying Corps to serve as an gunner/observer, being appointed a flying officer (observer) on 21 June 1916,[REF] but soon trained a pilot, and was appointed a flying officer on 21 November 1916 [REF].
On 1 April 1918, the Army's Royal Flying Corps and the Royal Naval Air Service were merged to form the Royal Air Force, and Stevens was appointed a captain in the new service that day [REF].