In recent years, global fascination with UFOs has reached new heights. But according to Pavel Poluian, a Russian physicist and philosopher with a background in geophysics, these sightings may have a more Earth-bound explanation.

In his letter to anomalien.com, Poluian claims that UFOs—or at least many of them—are advanced espionage devices developed by the United States during the Cold War, featuring plasma-driven propulsion systems that mimic the characteristics of otherworldly crafts.

Poluian, who has published multiple works debunking pseudoscientific theories, including “The Elimination of UFOs” and “The Hunt for UFOs,” explains that he believes these crafts were part of a secret U.S. military project, initiated shortly after WWII.

This project, he claims, aimed to develop aircraft using an unconventional propulsion system that generated lift via high-frequency vibrations.