Stewart served in the
Royal Flying Corps, and gained his first two victories over German fighters on 1 and 3 August 1916 while flying with
No. 20 Squadron RFC as an
Air Mechanic 2nd Class observer in the front seat of a
F.E.2b. He then trained as a pilot, and Corporal Stewart was awarded Royal Aero Club Aviator's Certificate No. 3958 after soloing a Maurice Farman biplane at the Military School at
Brooklands on 7 December 1916. and appointed a flying officer. His first victory as a pilot came on 6 January 1918 while flying an
Airco DH.4 for
No. 18 Squadron RFC. On 6 March 1918, he destroyed a
Pfalz D.III and drove three other German fighters down out of control. He continued to score steadily until 27 March, when he achieved his eleventh victory. On 25 March 1918 Stewart was appointed a
flight commander with the temporary rank of captain. He went on to gain another victory on 28 May, and scored double victories on 30 May and 11 June 1918. Fifteen of his triumphs were over enemy fighters; he destroyed eight and drove seven down out of control. He also destroyed an enemy two-seater. Among his observer gunners were fellow aces
Lewis Collins and
William Miller. On 1 November 1918 he was awarded the Distinguished Flying Cross. :Lieutenant (Temporary Captain) David Arthur Stewart, MC, Royal Air Force ::"An able leader, conspicuous for initiative and dash. He has destroyed three enemy machines, and has, in addition, taken part in numerous bombing raids, reconnaissances and photographic flights. In the majority of these he has been leader, and frequently in order to obtain accurate information he has led his flight at very low altitudes."
List of aerial victories ==Post-war career==