The Baade 152
This German-built plane was built with the design of a bomber plane. The plane had characteristics that would have been great for a bomber plane, but not for an actual airline aircraft. Its test run crashed and killed every crew member on board after only two flights. The prototype was canceled in 1961 and is the only aircraft that was ever built in East Germany.
The Rockwell XFV-12
Designing the first type of airplanes must have been a difficult concept to bear, but by the 1970s, you’d think the design would be strong enough to ensure that one of the top airline companies wouldn’t mess up so badly. However, when the Rockwell XFV-12 was invented, that proved the thought to be incorrect. It had a unique design and interesting features, though it never took off for a flight.