What happened
On the afternoon of January 7, 1948, the Kentucky State Police reported a large, round object in the sky to Godman Field near Fort Knox. It was also seen by personnel in the control tower, including the base commander. Four National Guard P-51 fighters were flying nearby and were ordered to take a look. The flight leader, Captain Thomas Mantell, reported a metallic object “of tremendous size” and began to climb. His plane had no oxygen equipment, and the other pilots turned back. Mantell climbed above 7,500 meters (24,600 feet), probably lost consciousness from hypoxia, and his aircraft crashed on a farm near Franklin. The pilot was killed instantly.
Witnesses
Captain Thomas Mantell and the other pilots of his flight, Godman Field personnel, state police officers, and Kentucky residents.
Explanations and hypotheses
At first the military claimed that Mantell had been chasing the planet Venus. Today it is widely accepted that it was a stratospheric balloon of the Navy’s Project Skyhook – then secret, huge, and shining in the sunlight – launched a few days earlier and carried by the wind over Kentucky. These balloons were little known even to military pilots, which explains the impression of a “huge metal object.”
Explained The phenomenon has a widely accepted, down-to-earth explanation.
More: Wikipedia (en)