In 1929, he was appointed Deputy Controller of Aviation, serving under Horace Brinsmead. When Brinsmead was incapacitated in 1931, Johnston was acting Controller, until he took the office in 1933.
In 1929, he was appointed Deputy Controller of Aviation, working under Horace Brinsmead. When Brinsmead became unable to perform his duties in 1931, Johnston temporarily assumed the role of Controller before taking it permanently in 1933.