Champion air racer "Speed" Leslie is facing his two greatest challenges. On the racing circuit, his dominance is jeopardized by a feisty female pilot, Brenda Gordon, whose interest in Leslie goes beyond simple competition. Back on the runway and in the hangar, he finds himself in a deadly confrontation with a ruthless gang of aircraft thieves. The outlaws' biggest heist involves an experimental flying machine known as the Mercy Plane, which can take off and land almost vertically, making it a perfect rescue vehicle. When Speed discovers that Brenda's brother is linked to the gang, he puts in motion a daring plan to force the criminals into the open.
James Dunn and Frances Gifford, who play the romantic leads in this exciting aviation film, were newlywed husband and wife when Mercy Plane was filmed in 1939, and exhibit a playful chemistry here. Dunn later won an Oscar for Best supporting actor for his work in A Tree Grows In Brooklyn (1945). Gifford is today best remembered for her starring role in the 1941 serial, Jungle Girl.