Lieutenant Droste wants to build an airstation in the middle of the ocean to allow pilots on intercontinental flights to refuel and repair any damage to their aircraft. With the help of the pilot Ellissen, he manages to win the support of the Lennartz-Werke for the project. Ellissen, who has taken up with the owner's sister Claire Lennartz, shies away from marriage and seeks new adventure. After two years, the platform has become a city on the ocean, with runways, hangars, hotels, and shopping centers. During a storm, the connection to the platform is severed. The last sounds to come over the telephone were gunshots and screams. The weather clears and the best pilots immediately head for F.P.1. Ellissen, in a lovesick depression, is convinced by Claire to accompany her to the platform. Their plane crashes on the island but they survive. The crew of F.P.1 has been the victim of a saboteur, who knocked them out with gas. Before chief engineer Damsky fled in a boat, he opened the valves, causing a danger that F.P.1 will sink. Claire finds the badly injured Droste and takes care of him. Ellissen has to recognize that Claire is slipping away from him. After a short time, he pulls himself together and takes a plane out to get help. He sees a ship, jumps from his plane, is taken aboard the ship, and calls for help via radio. A fleet of ships and planes are sent to rescue F.P.1.