Their president, William Craft (Robert Walker), hires a masked and mysterious airman, known only as "Pilot X", who also makes plans to steal those inventions for his own use.

The attacks are largely aimed at stealing Baker's exclusive rights to the "Aerometer", invented by James B. Joyce (C. H. Allen), a new navigational instrument that makes flying safer in all sorts of weather, even at night.

"World-famous aviatrix" Fawn Nesbitt (Dorothy Talcott), who hopes to become the first female pilot to fly around the world, becomes concerned when Baker's aircraft begin crashing.

Their efforts always seem to be known to the mysterious Pilot X, and suspicion falls on Perkins (Arthur Morrison), Joyce's butler, who is always nearby when plans are being discussed.

[7] Additional features include a commentary track by historian Richard M. Roberts, Flying Cadets (1928), a 2-reel United States Army Air Corps documentary film short, and a gallery of original The Mysterious Airman posters and lobby cards.