In early 1948, the Godman Army Airfield at Fort Knox, Kentucky received a number of reports from the Kentucky State Highway Patrol regarding an unidentified flying object. It seemed that people kept seeing a circular object, between 250 to 300 feet in diameter, hovering in the sky. It wasn’t just cranks who kept calling either. On January 7th, around 1:45 p.m., Sgt Quinton Blackwell was in the control tower at Fort Knox when he saw a white object which appeared to have a red border underneath when viewed through binoculars. It seemed to stay still for over an hour before disappearing. Over at the Clinton County Army Air Field in Ohio, observers described the craft as “having the appearance of a flaming red cone trailing a gaseous green mist”. A report from the Lockbourne Army Air Field stated: “Just before leaving it came to very near the ground, staying down for about ten seconds, then climbed at a very fast rate back to its original altitude, 10,000 feet, leveling off and disappearing into the overcast heading 120 degrees. Its speed was greater than 500 mph in level flight.”

At the point there were four P-51 Mustangs from the 165th Fighter Squadron Kentucky Air National Guard already in the air. They were ordered to intercept the object, and their approach was keenly monitored by Sgt Blackwell who remained in radio communication with them. One of the planes was low on fuel so the pilot decided to turn back. Thomas Mantell, and his two companions, continued the pursuit. There is some debate as to what Mantell actually reported to the control tower. In Michael D. Sword’s book ‘Project Sign and the Estimate of the Situation’, it is alleged that he described the object as being metallic and of tremendous size. Others dispute this.

The object was in a steep ascent and the pilots were ordered to level their altitude so they could get a clearer look, as it was some distance ahead and appeared indistinct. This was in part due to the fact that only Lt. Albert Clemmons had an oxygen mask, and even his supply was low. The pursuit was called off at 22,500 feet, but Mantell disregarded this and continued. As most people know, there comes a point where there is little breathable oxygen in the atmosphere. Mantell reached this point once he crossed 25,000 feet and it is believed that he blacked out. Witnesses reported seeing his plane caught in a downward spiral, eventually crashing at a farm close to Franklin, Kentucky.

When firemen pulled Mantell’s body from the wreckage, they noted that his watched had stopped. By that time, the flying object had disappeared. The case received widespread attention and rumors soon began circulating that Mantell had been shot down by whatever he had been chasing, even though there was no evidence to support this. Initially, Air Force investigators concluded that Mantell had misidentified the planet Venus as a UFO. However, astronomers from Project Sign quickly pointed out that, although Venus would have been in a favorable position for that theory, the planet would have been nearly invisible to observers. To this day, the cause of Mantell’s crash remains officially listed as undetermined.

One suggestion, by Dr. J. Allen Hynek, was that Mantell had in fact misidentified a US Navy Skyhook weather balloon. These were a secret project at the time so none of the witnesses would have been able to identify what it was. They were also made of reflective material, which could explain Mantell’s assertion that the UFO appeared metallic. In addition, it was later learnt that Skyhook balloons had been launched on January 7th 1948 in Clinton County, Ohio. It is theoretically possible that one of these could have been caught up in the wind currents. Skeptics also point to Mantell’s inexperience as a possible factor in the crash. Mantell had a total flight history of over 2,000 hours and he had distinguished himself at the Battle of Normandy. However, he was rather new to the P-51.

Whatever the case the fact remains that Thomas Mantell saw something that made him throw caution, and good sense, out the window. To this day, no one has been able to conclusively say what that was. Up to that point, the public wasn’t too concerned with tales of UFO sightings. Historian David Michael Jacobs argues that Mantell’s death was a turning point. A man had died in the pursuit of what appeared to be an unidentified flying object. The public started to question not whether extra-terrestrials existed but whether or not they could be hostile.