As the well-known story goes, on January 7, 1948, Thomas Mantell and three other pilots were flying near Fort Knox when they were asked by the control tower to check out a UFO seen in the area. One plane was running low on fuel and had to land, but the other three complied.

Suddenly, the control tower lost communications with the planes. Two later reported they had had no success, but Mantell evidently gave chase. A witness claims to have seen Mantell go to a very high altitude, then begin circling and fall into a dive. Halfway down, the plane exploded. It is believed that Mantell flew too high and, lacking oxygen for such flight, blacked out. Several other witnesses reported seeing a strange object in the sky that night.

Mantell was a World War II pilot who fought in Normandy and many other battles. A plaque has been erected at the site of his crash in Franklin, Kentucky.

-Lexington Herald-Leader: Kentucky decorated military pilot died pursuing UFO
(link courtesy The Anomalist)