Did the Nazi's bild the UFO

Many of the UFO sights in the 40s can be explained. The flying saucer could simply have been experimental military aircraft.
This is how some of the secret nazi weapons looked like:

It is obvious that a common person who saw that believed it was of extraterrestrial origin. And as it was a secret weapon the Nazi government of course wanted people to believe this.

Later after the war people like Werner von Braun continued building such kind of UFO (Air force / not alien) aircraft in the USA.