When Waldo is recounting his fight with Kessler at the start of the movie, he mentions that his guns jammed and Kessler, seeing that he was helpless, saluted then flew away. This actually happened to Ernst Udet (on whom Kessler is based) when flying against the French ace Georges Guynemer in 1917, only it was Udet (at that time inexperienced) who had the jam and Guynemer (a high scoring ace) who let him go.
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