The Messerschmitt Me 163 Komet
This aircraft was equipped with a rocket booster that was meant to intercept and destroy any enemy aircraft. It could reach up to 100 mph, which was much faster than any other plane at the time. Of course, it was all too good to be true, and the leaky fuel tank became a huge problem. There isn't much competition when your plane can't stay up in the air for more than 3 minutes!
The Noviplano
At first glance, this looks like a building. It's a plane! It was designed by Italian engineer Caproni during the 20s. The Noviplano, fitted with ten wings and engines, was designed to fly nearly a hundred passengers from Italy to America. It never made it out of Italy.