Educated at Loretto School and the University of Glasgow, Dunn joined the Royal Air Force in March 1933.

A collision with another Avro 504 resulted in the deaths of the other aircraft's pilot and the second person flying with Dunn.

[10] A notable battle occurred on August 8 1940 over Bir al-Gubbiyy, Libya, when Dunn lead a flight of three 80 Squadron Gladiators as bait for Italian fighters.

204 Squadron, then returned to the United Kingdom and became Aide de Camp to Marshal of the Royal Air Force Lord Trenchard in 1942.

[10] Dunn received a knighthood in August 1950[12] and went on to be an instructor at the NATO Defence College in 1951 before becoming Group Captain, Plans and then Air Commodore, Operations at Headquarters RAF Fighter Command in 1953.

[1] His final posting was as Air Officer Commanding-in-Chief of Flying Training Command in 1964 before retiring in 1967.