Dr. Jacques Vallee is a French-American computer specialist with a background in astrophysics and had written what I think are the finest books on the UFO phenomena.
I'd like to point you to this interview with him where he discusses his views. They are quite different then what you might expect.
Here is a sample..
But by 1969, when he published Passport to Magonia (Regnery), Vallee's assessment of the UFO phenomenon had undergone a significant shift. Much to the consternation of the "scientific ufologists" who had seen him as one of their champions, Vallee now seemed to be backing away from the extraterrestrial hypotheses and advancing the radical view that UFOs are paranormal in nature and a modern space age manifestation of a phenomenon which assumes different guises in different historical contexts.
" When the underlying archetypes are extracted," he wrote, "the saucer myth is seen to coincide to a remarkable degree with the fairy-faith of Celtic countries … religious miracles… and the widespread belief among all peoples concerning entities whose physical and psychological descriptions place them in the same category as the present-day ufonauts."
The complete interview..http://www.ufoevidence.org/documents/doc608.htm