The Swedish Ghost Rockets (1946)
Starting in February 1946, more than 2,000 sightings of rocket- or missile-shaped objects were reported across Sweden and neighboring countries, 200 of them tracked on radar. On July 19, a witness watched one of these gray, winged craft crash into Lake Kölmjärv with the sound of an explosion — yet no debris was ever found in the lake's waters.
Witnesses
thousands of witnesses, military radar
Why it endures
One of the very first mass UFO waves of the modern era, predating even Roswell and Kenneth Arnold, with hundreds of corroborating military radar detections.
Official version (contested)
Theories range from Soviet tests of captured German V2 missiles to simple meteors, with no explanation ever officially confirmed.