The Rockwell XFV-12
There was a race among the world's superpowers to create the best aircraft. The Rockwell had some promise for Americans that they would be the first to create a monster aircraft, but they were mistaken. The design of it looks clunky and bizarre. Luckily, it never went into test flights...
The Tupolev Tu-144
This plane was supposed to be a "supersonic" airliner. This plane was presented in the 70s as the next best thing in aviation. Sadly, its first-ever test-flight ended in horror during the Paris Air Show. It had crashed and burned violently. It was given 50 more test flights before it was finally deemed irreparable and unsafe.