Revealing mistake: When Von Richthofen is shot down and crash-lands in the combat zone, German and British soldiers arrive and fight for possession of the Red Baron's plane. It is strange, though, that the German soldiers fire British Lee Enfield rifles instead of the German Mauser Gewehr 98.
Factual error: It is true that Richthofen was killed during an aerial battle with a Canadian pilot; but it was not by the pilot (in the movie, his counterpart Brown) himself, but by one of the Australian machine gunners on the ground (it is still not for sure which one of the gunners did it, though).