The movie was "The Eagle and the Hawk", starring Frederick March, Jack Oakie, and a young Cary Grant(Paramount, 1933). March was the shell-shocked and war weary two seater ace (he flew a DH9A painted up in fantastic camouflage) who keeps bringing back dead observers and eventually commits suicide. This movie has shown up on the Cable channel AMC every once in awhile, and is available on video from various outlets; I have it on tape and I consider it one of the better WWI movies. Interestingly enough,
Bogart Rogers, an American SE5a ace with No. 32 Squadron, was one of the screen writers. He had been trained under McCudden, and had certainly read McCudden's "Five Years in the Royal Flying Corps". March frquently tangles with a deadly German ace called "Green Tail", and when he finally shoots the German down , it is discovered that he is none other than - Voss ! Unfortunately, "Voss" wasn't flying a Fokker Triplane and the movie's in black and white, so it doesn't reveal any new clues about the color of Voss' cowling !!