The film was loosely based on a true story. Allied prisoners-of-war held at Colditz Castle constructed a similar glider under the noses of their captors, but did not complete the aircraft until after D-Day. Rather than use the glider to escape, the prisoners determined to use it to coordinate their actions with Patton's forces. As it turned out, the German garrison surrendered to the Americans without firing a shot.
During a prisoner roll call, the German guard calls the name "Hogan", a reference to Hogan's Heroes (1965), which also featured Don Knight. The name "Baer" is also called, a reference to Max Baer, who stars in the film.
Although the flight of the Colditz glider did not happen as originally planned, two full-sized replicas of the glider were built and flown to discover if the plan would have worked. In 1999 a full-sized replica of the Colditz glider was commissioned by British public-service television broadcaster Channel 4, and was test flown successfully in 2000 on its first attempt. Nearly a dozen of the veterans who had worked on the original more than 55 years earlier attended the flight. In March 2012, a radio-controlled, full-sized replica glider was built in the Chapel attic and was flown from Colditz for a second Channel 4 documentary. The unmanned replica was launched from the same roof as had been planned for the original flight. The radio-controlled replica made it safely across the River Mulde and landed in a meadow approximately 180 meters (590ft) below.
All of the main prisoner characters have last names that begin with the letters "A" through "D" so that they could be called quickly during roll call scenes.
Tom Skerritt plays a character named Orville. In an episode of Gunsmoke called The Moonstone 1966 he plays a character, Orville Timpson.