Stockton, CaliforniaMay 1952

On May 22, 1952, a group of about eight people at the Stockton Naval Supply Station in California watched a bright silver, rectangular object hang motionless in the sky for 25 minutes, then fade from view. The sighting took place at approximately 1240 (12:40 p.m.) and lasted until about 1305 (1:05 p.m.).

One observer, a civilian working at the Naval Supply Station, used an artillery surveying instrument to measure the object's position. He calculated that it was hovering at roughly 30,000 feet altitude, positioned at 350 degrees horizontal azimuth (roughly north) and 85 degrees vertical angle (nearly straight overhead). The witnesses reported that the object did not fly away, but simply vanished from sight. At the time, winds aloft were blowing at 20 to 30 knots from varying directions at different altitudes.

The Air Force checked whether any weather balloons had been released in the area during the sighting window. The Stockton Interstate Air Weather Station reported no balloon launches. However, some of the witnesses themselves believed the object was likely a weather balloon, based on their familiarity with balloon launches from the Stockton Airport. Radar operators attempted to intercept the object using two P-39 aircraft at approximately 1300 (1:00 p.m.), but the radar tracks faded before the planes made contact. The radar had picked up some unidentified contacts at 8,000 feet, though those were at a lower altitude than where the visual observers said the object was positioned.

The Air Force's official evaluation listed this case as unidentified. The file notes that the nearest scheduled balloon launch was at a San Francisco facility, and the witnesses' belief that it was a balloon appears in the case record, though the investigation could not definitively confirm that conclusion. The full case file, consisting of 10 pages, is reproduced below as held by the National Archives.