Air Hawks [1935]

Barry Eldon is the owner of an airline company that is competing with a rival company for a lucrative air-mail contract with the government. While the other company is bigger and more profitable than Barry's line, the rival owner has hired a scientist that has perfected a ray-machine that will cause airplanes that its ray is directed at to lose their engine power and crash. Thed government and the public are losing faith in Eldon's line before he, aided by Renee Dupont, can find out what is causing his airplanes to crash.