There is a nearly 1.0 correlation between folks that “see aliens” or at least believe in them and involvement in the occult.
Conversely, there are few cases (I don’t know of any) of Christians reporting alien sightings.
Demonic origin perhaps? Just conjecture.
Based upon other sources it sounds like Mitchell was involved in the occult at least on the periphery. His claim to having been remotely healed by a medium is not surprising. Once these people open the door to these fallen spirits they begin to have all types of strange encounters.
Perhaps Christians con't perceive them as, "alien", but rather miraculous or angelic. The Emperor Constantine saw the apparition of a cross in the sky (In Hoc Signi), and of course, the The miracle of the sun at Fatima, Portugaul was well documented, although of course, its cause has never been definitively been established as alien, demonic or miraculous.
Likewise, no less a Christian thinker wrote both fiction and serious philosophical postulation about the existence and moral nature of life on other worlds (and humorously speculated about how human vanity would lead us to proselytize on an Edenic world where the natives had actually obeyed God, and not fallen from grace.)
Oh...and while I suppose the author pre-dated Christ, my Bible includes a Book of Ezekiel. You may want to take a look at Chapter 1.
I’m a Christian. I’ve not seen an actual extraterrestrail (that I know of), but I have seen an extraordinary craft in flight that defied conventional aerodynamics and I would call it a UFO. What that craft did in flight is still beyond our conventional flight capabilities, so it would stand to reason that it was extraterrestrial ... from our future or an ‘off-world’ civilization, I haven’t a clue. And before you poopoo the notion of extraterrestrails, remember there ARE Angels and demons and they exist in some where/when you/I/we cannot access readily, AND there are extraterrestrial sightings throughout the Bible narrative.