The Birdmen (1973)

They used to boast there were only two ways to escape from Hitler's Beckstadt prison... to die...or to sprout wings

During WWII an American soldier sent to Norway to help with the escape of a scientist working on the atomic bomb for the Germans. Before they can escape they are captured and sent to a POW prison camp in an alpine castle. Cook must find a way to escape with the scientist before the Gestapo discover the Norwegian's true identity and convinces the other prisoners to build a two person glider in which they plan to escape.