UFOs are Unidentified Flying Objects, but due to fake conspiracies, attention seekers, and government cover ups, it has grown into a science fiction phenomenon.
The drug culture and atheists appreciate the UFOs stories, because it helps bring conscience to their belief that we are evolving to space aliens, and that their are other planets that are more advanced than earth. (or something pretty close to this) Where atheists are abundant, than pseudo-science is as well.
The government has top secret air force facilities like Area 51 in Nevada. Sometimes accidents happen or sightings of new air craft is spotted, so officials put out fake stories for the masses. Weather balloons or almost believable stories about spaceships crashing, with alien life form pictures. The government may use this agenda to push a greater hoax in the future, so be cautious.
Also, unfamiliar weather patterns combined with folklore helps spread the misinformation, not to mention tremendous overrated rock bands like, The Foo Fighters. I recently found out about ball lightening by learning about the Concave Hollow Earth, I will leave a video below to explain what ball lightening is.
I don't believe in space aliens, little green figures with space suits, or multiple universes outside of Earth. This is all to promote science fiction and Darwin's theory, well, at least that's what I believe anyways. As far as nephilim or fallen angels, they can't hurt you, unless you take your eye's off of Jesus Christ. Sure, man can kill the body, but they can't kill the soul.
Almost forgot about crop circles, that is normally done by stoner college students, who like to prank farmers, and others.
I believe ball lightening explains the stories you heard from World War 2 pilots. Don't believe the History Channel or the public school system, it's paid for by special interest groups, that keep the masses in a coma like state.