While I can't answer this question for the Air Battalion Royal Engineers, I can answer it from the point of view of the Royal Navy, whose air wing was integrated into the RFC along with the Air Battalion. The RN's first pilot was George Colmore, a lieutenant who joined the Royal Aero Club (RAeC), paying for training out of his own pocket. He obtained his pilot's certificate on the 21st June 1910. Colmore's success established links between the Royal Aero Club and the Navy. In November of that year, the RAeC offered the Admiralty and War Office use of its aerodrome at Eastchurch in Kent, at the instigation of one of its senior members, Francis McClean. The War Office chose not to take advantage of this offer, but the Navy did. Along with the use of the airfield at Eastwich, the RAeC also provided two aeroplanes, and the use of its members as instructors. A call for volunteers was sent out on the 6th December 1910, with it being required that pilot candidates were unmarried and able to pay the fees of the RAeC. Four candidates were chosen for pilot training at Eastchurch. Three of these were Royal Navy lieutenants - Charles Sampson, Arthur Longmore and Reginald Gregory, while the fourth, Eugene Gerrard, was from the Royal Marine Light Infantry. They began training at Eastchurch from the 1st March 1911, while they were on the books of HMS Actaeon, the RN's torpedo school at Sheerness. While they were undergoing training, other officers were paying for their own training with private flying clubs, with Lieutenant Wilfred Parke training at Brooklands and Lieutenant Richard Bell Davies training at Hendon (the latter paid £50 for the privilege, along with a £25 deposit for damages). Samson, Longmore and Parke graduated in late April 1911, while Gerrard, Gregory and Davies following in May. In November 1911, Commander Oliver Schwann, who had bought an aeroplane with friends and converted it into a seaplane, made a short flight in it, despite not having any previous experience or training. This flight would prove disastrous for his aircraft, though Schwann would survive. Meanwhile, plans were underway to establish a Naval Flying School at Eastchurch. The first course at the new school began on the 2nd March 1912, just over a month before the establishment of the RFC.

The formation of the RFC combined the naval pioneers and the Army's experimental force into a single organisation, under the control of the Army. However, it did not include the school at Eastchurch. The Royal Navy did not wish to see the entirety of its access to aviation under the control of the Army, and saw this as a vital way to maintain this. Instead of putting Eastchurch under the RFC, a new school (the Central Flying School), was formed at Upavon with both Army and Navy instructors. This was under the command of Godfrey Paine, who had been captain of Actaeon when the early RN pioneers had been training there (his adjutant was Hugh Trenchard, who would later go on to play a major role in the foundation of the RAF). The instructors were drawn from a mix of the early Army and Navy pioneers and from instructors from the RAeC.