1794 Top Secret Project
Secrets are kept almost everywhere, and the Air Force knows perfectly how to do this for the US military – except for this one now in the public’s eye. This mysterious-looking supersonic flying saucer never came to light even though it had a blueprint.
High-Speed Train
The Schienenzeppelin is Germany’s first high-speed train and was a phenomenal invention at the time. This train was recorded to go up to 143 miles per hour, and whether it was used for the public or private mission, no one knows.