Rusby was appointed Second Lieutenant from
Flying Officer Observer on 16 September 1916. However, his seniority dated from 29 September 1916. Rusby began his aviation career as an observer/gunner in two-seater reconnaissance aircraft in
No. 22 Squadron RFC. He was wounded three days later. However, the wounding did not prevent him from undergoing pilot's training. He was then confirmed as Lieutenant 1 June 1917, but ordered to surrender his Temporary Captaincy. Then he was promoted Captain as of 4 July 1917. In October 1917, Rusby was transferred to
No. 29 Squadron RFC to serve as a
flight commander. He gained his first aerial victory in a
Nieuport single-seat fighter on 16 December 1917, driving down a German
Albatros D.V fighter in the vicinity of
Roulers. He also upgraded to a
Royal Aircraft Factory SE.5a, which he used for six single victories in May 1918; one of these was a triumph shared with fellow aces
Francis James Davies and
Charles G. Ross. Rusby's final tally was five enemy planes destroyed (three of which he set afire), two driven down out of control, and one captured. Rusby was honoured with a
Distinguished Flying Cross on 3 August 1918. ==Honours and awards==