🇺🇸 USAF — Project Blue Book
In December 1955, near Bergen Park, Colorado, two witnesses reported a round object that appeared the size of a match head at arm's length. They estimated the object to be the size of a large bomber and at around 10,000 feet altitude. The object was described as silver, similar to an aircraft in color. Their attention was drawn by a jet passing overhead, and then they saw the object, which initially moved slowly but then appeared to gain speed. They estimated its speed to range from that of a jet to 1,000 mph.
The main source of information was a telephone interview with the witnesses, whose reliability was considered questionable. Despite efforts to contact the jet pilot, no positive results were obtained. The witnesses admitted the possibility that the object was a high-flying aircraft, but the lack of contrail and the increase in speed convinced them it was not a conventional aircraft. Ultimately, the case was classified as "possible aircraft".