Refresh my memory.Didn't Cooper advance the idea that the UFOs and aliens were associated with MAJIC-12 and that the aliens were better identified in some cases as demons, or fallen angels as historicaly referenced. The Majesty/Majestic/Majic/MAJC/MJ-12 theories having been founded back by Truman then Eisenhower after making an agreement between man and the devil (aliens) to trade facilities and access to bio material to perform genentic research by the aliens in return for UFO hi-technology,...and the mother of all conspiracies continued from there?
Later, other CTs tended to merge into these, like JFK assasination, Dulce Wars, Underground caverns, Nazis in South America and the Antarctic, many of the X-File detailed themes seemed to have been born by his work.
It's my understanding that Cooper wrote "Majestytwelve" which puts "alien-sightings" under the catagory of secret military weapons. Later, it seems, for whatever reason, others co-opted the name Majic-12, which purports to tell about government cover-ups of actual alien space ship landings, etc.
Just scanning the web, I found a site which gives you a good take on his view of E.T.s -- www.williamcooper.com/area51.htm.
His book, "Behold a Pale Horse," is an interesting read, and I think it's a shame he's dead.