Believe it or not, the
BBC reported that after the war attempts were made to make Spitfires break the sound barrier. Like Hardy, one pilot was able to successfully glide and navigate his plane down safely after the propeller had broken off completely.
What’s more, a
USA Today Q&A with a pilot posed the question of how far a jetliner could glide if the engine quit at 30,000 feet. While it would vary in the wind, the pilot estimated that it could travel for another 100 miles. An older, smaller plane like the Spitfire would cruise at only 20,000 feet, and it’s 78.5 miles from Dover, England to Dunkirk — so even after the Spitfire’s dogfights, the distance it traveled in the film without a propeller was well within the range of possibility.
There's also examples during the war of pilots being able to glide their spitfires of upto 15 miles. One thing I can commend Nolan on is getting the details right, granted they're added some flair but they're never completely hollywood, there's always a dose of possibility behind it.