Forbes AFB, KansasJuly 1957

On July 17, 1957, an RB-47 reconnaissance aircraft (a modified B-47 bomber equipped with electronic surveillance gear) encountered an unidentified object over northern Louisiana and Texas during a pre-dawn flight. The aircraft was crewed by six officers based at Forbes Air Force Base in Kansas. Over the course of about an hour and twenty minutes, the RB-47 crew reported multiple sightings of a bright light, and their onboard electronic monitoring equipment detected radar-like signals that appeared to move across their scopes in ways suggesting a nearby, moving target.

The crew's initial encounter occurred at 10:10 a.m. local time, when the pilot observed a very bright light with a bluish tint crossing in front of the aircraft from the 11 o'clock position and disappearing toward 2:30. Both the pilot and co-pilot witnessed this event. About twenty minutes later, the electronic countermeasures operators aboard the aircraft detected an S-band radar signal (operating at frequencies near 3,000 megahertz) with characteristics resembling the CPS-6B air defense radar then in use by the U.S. military. The signal moved upward and to the right on their display scopes as the aircraft flew, which the crew interpreted as evidence of an airborne object keeping pace with or maneuvering relative to them.

The RB-47 requested and received permission to deviate from its planned route to pursue the object. During the chase, the crew reported multiple colored lights and the electronic equipment showed what appeared to be two separate targets at one point. An air defense radar station near Dallas (code-named "Utah") briefly reported an unidentified target on its scopes, which the Duncanville station commander later officially denied. The pursuit continued for roughly an hour as the aircraft accelerated and changed course. The crew eventually abandoned the chase near Mineral Wells, Texas, due to low fuel. They headed north toward their base in Kansas, and the electronic signals faded as the aircraft neared Oklahoma City.

The Air Force's official evaluation was "unknown." However, the file contains a later analysis by electronics expert Philip J. Klass (published in 1971) suggesting a more conventional explanation. Klass argued that the bright light sighting may have been a bright meteor, and that the radar signals the crew detected likely originated from ground-based CPS-6B and FPS-10 air defense radars at Biloxi, Mississippi, and Duncanville, Texas, rather than from an airborne object. According to Klass's analysis, certain technical malfunctions or misinterpretations of the radar direction-finding displays could account for the crew's observations. The RB-47 pilot, Lewis D. Chase, later reviewed Klass's analysis and stated it provided "a plausible explanation for the events that happened to my crew that night in 1957."

The full case file, consisting of 56 scanned pages as held by the National Archives, is reproduced below.