The Lockheed Martin VH-71
Honestly, this plane had a pretty good design on paper. Augusta Westland and Lockheed Martin started to market this plane in the United States in 2002. This plane seemed to be so amazing that the Marine Corps even suggested it be used to transport the President! Unfortunately, the pricepoint moved from $6.1 billion to $11.2 billion just a few years later, which was not realistic.
The Bristol 188
No matter what you’re selling or doing, it’s always important that you are, at minimum, on-par with your competition. When Chuck Yeager invented the Bell X-1 in 1947, it prompted other people to try and create a plane similar to it. The British had their version which they called the Bristol 188, but there were many imperfections with the plane. Not only did the fuel tank leak during flights, but the plane could not take off until it reached a ground speed of 300 MPH.