Hard to pin down sometimes which we each judge as great movies. For me the production company's attention to detail plays at least some role. The 'devil's in the details' kind of thing. The movie can have all the right ingredients, yet one oopsie can spoil the overall quality and effect.
While studying the movie
Dunkirk, I noticed the accuracy of the B roll audio for the Spitfire aircraft. They, like the P-51, make a very distinctive sound- that Merlin engine sound is unique. Both the P-51 and Spitfire make similar sounds because of the similarity of the engines and the overall aircraft design. One difference is the open gunport whistle that's more common to the P-51. Hard to forget the sound of either aircraft.