Coombes was assigned to on 22 July 1917 as a probationary flight officer, and attended the training schools at Air Stations Chingford and
Cranwell, before being awarded his Royal Aero Club Aviator's Certificate at Air Station
Fairlop on 20 September. He was promoted to flight sub-lieutenant on 28 September, and posted to
HMS Daedalus in November. In June and July he was credited with shooting down ten more aircraft, bringing his total number of victories to fifteen. Coombes was awarded the
Distinguished Flying Cross (DFC) on 3 August, then returned to England to spend the rest of the war serving as an instructor at No. 204 Training Depot Station at
RAF Eastchurch. and spent the rest of the summer
barnstorming around the north of England in surplus
B.E.2's with
Charles Kingsford Smith before returning to City and Guilds College, to finally receive his Engineering degree in mid-1920. ==Engineering career==