Swedish military opinion on "Ghost Rockets"
Although the official opinion of the Swedish and U.S. military remains unclear, a Top Secret USAFE (United States Air Force Europe) document from 4 November 1948 (at right), indicates that at least some investigators believed the ghost rockets and later "flying saucers" had extraterrestrial origins.
Down below document get declassified only in 1997:
The document states: "For some time we have been concerned by the recurring reports on flying saucers. They periodically continue to pop up; during the last week, one was observed hovering over Neubiberg Air Base for about thirty minutes. They have been reported by so many sources and from such a variety of places that we are convinced that they cannot be disregarded and must be explained on some basis which is perhaps slightly beyond the scope of our present intelligence thinking. "When officers of this Directorate recently visited the Swedish Air Intelligence Service, this question was put to the Swedes. Their answer was that some reliable and fully technically qualified people have reached the conclusion that 'these phenomena are obviously the result of a high technical skill which cannot be credited to any presently known culture on earth'. They are therefore assuming that these objects originate from some previously unknown or unidentified technology, possibly outside the earth". The document also mentioned a flying saucer crash search in a Swedish lake conducted by a Swedish naval salvage team, with the discovery of a previously unknown crater on the lake floor believed caused by the object (possibly referencing the Lake Kölmjärv search for a ghost rocket discussed above, though the date is unclear). The document ends with the statement that "we are inclined not to discredit entirely this somewhat spectacular theory [extraterrestrial origins], meantime keeping an open mind on the subject"