In Genesis 6:4 there’s a description of giants born from the intercourse of angelic beings and Earthly women; similar activity between heavenly beings and earthly people is still described today.
The angel appeared to in his bedroom one night, resulting in the foundation of the Mormon religion. Some humans such as have suggested that they may be God’s own heavenly beings.
Some Christian literature suggests that UFOs are agents of the Devil, who they imagine as a subterranean lizard-man. These Christians believe UFOs are actually fallen angels sent from below to deceive innocent Earthlings.
A member of the branch of the told UFO researcher :
The only thing we can say is that an angel can sometimes be a UFO as well as a craft being a UFO. And so, unless you develop yourself enough, you might be insulting some angel, calling him a UFO.