German WWI monoplane really did exist
No one discusses the prototype World War I Imperial German Fokker VIII monoplane that was depicted in the movie, "The Blue Max", since most people assume it to be movie fiction. But in fact it did exist.
However, for some odd reason, the movie's prop department came up with what looks to be something that resembles the post-war, "Spirit of St. Louis" monoplane. Charles Lindburgh flew his special-built monoplane across the Atlantic in his famous solo flight.
In the last year of World War I, fighter aviation technology and aerospace science were advancing quickly. Aviation experts estimate that fighter plane technology and aerospace science advanced 15 years in just 4 years of aerial combat. German aviation science experts foresaw the time of the higher-performance monoplane fighter. They put their theories to practical test with the new Fokker VIII parasol wing monoplane. The type is called, 'parasol wing' because the single wing is mounted on top of the fuselage, instead of below. The next twenty years of aviation science would prove the parasol wing to be a technological and fighter aviation dead end. Parasol winged monoplanes could not take the stress of high-G maneuvers in the sky.
This was the point of the unstable German monoplane being pointed out by the plane's designer to the imperial German field marshall. But whoever researched the Fokker VIII for, "The Blue Max", did his job. In real war history, the Fokker VIII was indeed rushed into mass production by a desperate Imperial German government, facing war exhaustion and overwhelming enemy numbers and resources, now that the Americans were pouring into France. And as the movie pointed out, the first Fokker VIII monoplanes did suffer catastrophic wing mounting failure. As a result, the whole Fokker VIII monoplane fleet was grounded during the follow-up investigation. The answer was to quickly reinforce the parasol wing, which apparently fixed the wing failure problem. But precious time had been lost. There were only mere weeks left before the November 1918 Armistice. Subsequently, the Fokker VIII does not have much of a fighting record to post.
The monoplane's chief designer had already detected the weak wing stability problem without knowing the exact technical cause. This technical fault, along with the inherent structural weakness of parasol-mounted wings, and then put through swirling fighter maneuvers by an eager but unknowing Lieutenant Stachel (George Peppard), made the consequential crash almost inevitable. The man was deliberately sent to his unknowing death, and he ecstatically embraced it as shown in the movie. Lieutenant Stachel has achieved everything he desired in life. He already had the blond, blue-eyed, tall, handsome boy looks. He got to bed the beautiful, blonde Countess Krugerman (Ursula Andress at the height of her beauty), but more, he achieved beloved celebrity status and the social elevation he so desperately craved. But it all proved fatally ephemeral.
SUMMARY. Parasol winged monoplanes exist today as small sport and recreation airplanes. There's nothing unsafe about a parasol winged airplane. It's just that you're not going to find yourself maneuvering around the sky like it was a P-51 Mustang or a A6M5c Japanese Zero. You're just going to cruise slowly around the sky, enjoying a fantastic view of Mother Earth because parasol wing airplanes don't obstruct the view below. The 1918 German aviation engineers knew there was something unstable about the new Fokker VIII monoplane and needed more time to work the bugs out, which they didn't get. More, the parasol wing monoplane proved ill-adapted to fast fighter airplane aerial maneuvers. Why the movie's prop department couldn't manufacture some reasonable facsimile of the historical Fokker VIII is a mystery. Google the Fokker VIII and you can find a lot of information and photos of actual reproductions.