While in France in 1915 he transferred to the Royal Flying Corps. As there were no places available for pilots in the flight school, he chose to be an observer. On 1 September, he reported to 21 (Training) Squadron at Netheravon for elementary air instruction. The first aircraft he trained in was the Avro 504, flown by Roger Neville. Bishop was adept at taking aerial photographs, and was soon in charge of training other observers with the camera. The squadron was ordered to France in January 1916 and arrived at Boisdinghem airfield, near Saint-Omer, equipped with R.E.7 reconnaissance aircraft. Bishop's first combat mission was as an aerial spotter for British artillery. At first, the aircraft could not get airborne until they had offloaded their bombload and machine guns. Bishop and pilot Neville flew over German lines near Boisdinghem and when the German howitzer was found, they relayed coordinates to the British, who then bombarded and destroyed the target. In the following months, Bishop flew on reconnaissance and bombing flights, but never fired his machine guns on an enemy aircraft.