Bill Cooper said that he saw UFOs in the navy near Pearl Harbor. in the 1960's.He says they are man made.He says they are planning to maybe one day have a fake invasion to unite the world in fear.He also was tricked himself with fake alien info for many years,it was put on his desk when he was the person who briefed the pacific fleet admiral(or similar).
There is also a new way of flight that may be used. Gyroscope flight.
The interesting thing is a university physics class I was shown this in 1973.
Eric Laithwaite tried to do similar from about 1973-1998 but never succeeded . He was ridiculed for trying to do something that had been done already.
There was a BBC youtube on how he was the only royal society lecture that they would not print his lecture, it seems youtube took it down.