No such thing as aliens, or monsters, in God's creation. Demons yes, but not aliens.
I'm surprised that no one has mentioned Ezekiel 1 about what he saw that was the color of amber, which in the Hebrew means 'highly polished spectral metal' per Strong's Exhaustive Concordance. It had legs like a calf (i.e. landing gear), and when it went it turned not (i.e., was round shaped), etc. And the most amazing thing Ezekiel saw was that GOD's throne was on it.
So just as we have good and bad people driving cars on the road today, in the Heavenly dimension there's good and bad angels flying those craft.
I believe the demons, disguising themselves as aliens, have long since been in contact with the powers that be in this world. We should not be surprised that secret Lucifer worship can be found among many of the higher powers in governments, corporations, finance, politics, and even religion. Just back in the 1930's, there were at least twelve initiate secret societies that met in Lyons, France which is the seat of what they call The Grand Orient. They together made up an organization abbreviated as F.U.D.O.S.I., a French title that meant something like, United Federation of Initiatic Orders. Freemasonry was a member, as was the Rosicrucian Order (AMORC). And just as the British Mason John Robison revealed in his 1798 book
Proofs Of A Conspiracy, the Illuminati order had been created by an orthodox Jewish professor Adam Wieshaupt that taught at Ingolstadt university in Austria, with his Illuminati Order having infiltrated the highest levels of continental Masonry, with its purpose being to overthrow the governments and royal families of Europe, and Christianity. (free at archive.org --
Proofs of a Conspiracy : John Robison : Free Download, Borrow, and Streaming : Internet Archive)
I'm also surprised that so many brethren have not put two and two together about Satan and his host of angels coming to this earth in OUR earthly dimension, as written in Revelation 12:7 forward. It says there because of the war in Heaven between Michael and his angels vs. Satan and his angels, that then there will no more be a place found for Satan and his angels in Heaven. That means Satan and his angels are to be booted... out of Heaven literally, and that leaves only one other place he can go, and it is to this earth where we are, in OUR dimension. Now link that to the start of the "great tribulation", and maybe you will understand what the coming great tribulation is actually going to be about!