Between Fresno-Merced, Calif, April 1958April 1958

In April 1958, a pilot and copilot of two F-100C fighter jets spotted an object they could not identify in the sky between Fresno and Merced, California. The pilots were flying at 45,000 feet at roughly Mach 0.8 speed. They were investigating a large weather balloon that was floating at approximately 150,000 feet when they saw something else entirely. The object appeared as a small, white, circular shape to the naked eye, no larger than a pea held at arm's length. The pilots watched it make a sharp 180-degree turn near the balloon, then streak rapidly toward the Pacific Ocean on a south-southwest heading. The entire sighting lasted about four to five seconds.

The two pilots had solid reputations for reliability, according to Air Force investigators. The weather conditions were clear with excellent visibility at the time. Air Force intelligence officers noted that no known aircraft, balloon, or other object could account for what the pilots saw. However, the investigation took an interesting turn when the U.S. Air Force disclosed that a U-2 spy plane, then engaged in a classified project, had been in the general area at the same date and time. The U-2 pilot also spotted a balloon, and the U-2 did make a turn in the area where the F-100 pilots reported the object. Despite these details, the Air Force file does not clearly state whether the unknown sighting was identified or resolved.

The complete case file, comprising eight pages of the original microfilm records, is reproduced below as held by the National Archives.