Von Ryan's Express (1965), directed by Mark Robson.
Shot down in Italy, American flyer Frank Sinatra is dumped into a mostly Brit POW camp, where he takes command as senior officer. Some amount of conflict here, but when Italy surrenders they have a chance to break out, evade the Germans and hijack a train to freedom.
It's exciting! Obviously improbable without being totally fantastic. Trevor Howard is good as the sour but stalwart British commander, and Edward Mulhare is a hoot as their padre who speaks German and looks swell in the uniform.
The location shooting helps a lot. The final scene where Frank runs for the train is an iconic clip in studio retrospectives.
Jerry Goldsmith score.
From from the 10-disc "Frank Sinatra Film Collection."