De Bonnefoy was a pre-war cavalryman who volunteered for aviation as soon as the war began. His first flying assignment was to Escadrille 101 to pilot a Voisin. He was removed from the front for a spell as an instructor, then successively assigned to two Nieuport squadrons, Escadrilles 68 and 65.
He scored his first aerial victory on 2 July 1916, and gradually accumulated five by 5 November 1916.
The much traveled ace would be temporarily withdrawn for a rest, then assigned to Escadrilles 15 and 31 before ending the war in 23. De Bonnefoy remained in the military postwar.
He became an Officer of the Légion d"honneur before dying on 27 September 1946. for feats of war.