N Of Halsingberg, Sweden, December 1958December 1958

On a December 1958 night near Halsningberg, Sweden, two men claimed they had encountered and fought with alien beings who landed in a spacecraft. According to the report card, the Air Force noted there was "no evidence to substantiate" the story.

The case landed on the desk of the U.S. Air Attache in Stockholm, who asked the U.S. Air Force's European intelligence team to work with Swedish Air Force officers to evaluate what had happened. An Air Force intelligence representative who examined the case concluded it was a deliberate hoax. No full intelligence report was written. Instead, the Air Force simply filed a verbal summary from the representative after he returned to headquarters.

Swedish Air Force intelligence had already grown skeptical of UFO reports in their country. Many earlier sightings, they believed, were either hoaxes or attempts by Soviet forces to test Swedish radar and other defense systems. The one exception was a strange case from October 1957, when witnesses reported seeing "angel's hair," a silky substance drifting over a Swedish island. Chemical analysis showed it was spun natural silk that had been mechanized and stressed. The Swedish Air Force asked the U.S. Air Force to help explain the phenomenon, wondering if it came from high altitude balloon bursts or other known sources.

The Air Force investigated the angel's hair case and found a similar occurrence in California in 1954, where residue turned out to be cobwebs. They suggested the Swedish sighting might have come from a nearby silk processing plant with a broken filtering system, or from unusual wind patterns carrying fibers from industrial mills. The full case file is reproduced below as held by the National Archives, containing 9 pages.