Codename Chessboard avi; a k a The Birdmen(1971)

During World War II, American soldier Harry Cook is sent to Norway to aid in the defection of a scientist working on the atomic bomb for the Germans. Before they can escape Europe, they are captured and sent to a POW prison camp in a high alpine castle on the German-Swiss border. Cook must find a way to escape with the scientist before the Gestapo discover the Norwegian's true identity. Cook convinces the other prisoners to build a two person glider that can fly to Switzerland. The race is on to complete the glider before the German guards discover the plane, and the Gestapo catch up with Cook and the scientist.