On January 7, 1948, during a routine patrol, Kentucky Air National Guard pilot Thomas Mantell encountered what he believed to be a UFO over Fort Knox, Kentucky. Reports indicated that locals observed a large, shiny, metallic object hovering in the sky, prompting Mantell to engage in a pursuit with his F-51 Mustang fighter plane. As Mantell ascended to investigate, he relayed his observations to air traffic control, describing the object and expressing the urgency of his mission. Unfortunately, during this ascent, Mantell lost sight of the object, and some reports suggest he may have experienced difficulties due to extreme altitude and potential structural issues with his aircraft.

The search for Mantell's aircraft commenced soon after he vanished from radar. Ground searches led to the discovery of the wreckage that tragically revealed Mantell had not survived. An investigation into the incident highlighted challenges in communication and the overall training of pilots in dealing with unidentified objects in the sky. Mantell’s pursuit became one of the first highly-publicized encounters with UFOs in the United States, further fueling interest and speculation regarding unexplained aerial phenomena.

This incident gained significant media attention, partly due to the fact that it involved a military officer and the elusive nature of UFO sightings in general. The crash served as a pivotal moment in the broader narrative of the phenomenon, leading to further government scrutiny and public fascination with unidentified flying objects in the post-war era. It also sparked debates within military and aviation communities regarding the handling of UFO sightings and the need for protocols in such unpredictable situations.