"[4][Note 2] Before the outbreak of the Second World War, British test pilot Peter Thurloe (Barry K. Barnes) is involved in an illicit love affair with his employer's wife, Dorothy Houghton (Joan Marion).

Scotland Yard Inspector Colonel Cairns (Felix Aylmer) is aware that the plans of a top-secret aircraft would be of great interest to an enemy.

[6] A Percival Vega Gull (G-AEYC) and Miles M.14A Magister I/Hawk Trainer III (L6908) were featured in the film, as well as a brief glimpse of a de Havilland Dragon Rapide.

[9][10] Spies of the Air was quickly relegated to "second feature" status, as the release of the similar themed Q Planes (1939), with a much better known cast, overshadowed the more modest production.

Hal Erickson wrote, "The flight sequences blend stock footage and newly-shot aerial scenes with acceptable expertise.