100 Mi East of Honshu Japan, May 1950May 1950

On May 19, 1950, two F-84 fighter pilots spotted an unidentified object in the sky 100 miles east of Honshu, Japan. Ground radar had first detected something in the area, and the pilots were guided toward it. At 10:40 a.m., they made visual contact with the object.

The pilots described what they saw as resembling a box kite in shape. They estimated its dimensions at roughly thirty inches by twenty-four inches. Both pilots reported that the object appeared stationary in the sky. They could see no visible means of support, like a parachute or wire, holding it aloft. The pilots kept the object under observation for twelve minutes, from 10:40 a.m. to 10:52 a.m.

The investigation that followed produced a possible explanation. At 10:00 a.m., just before the sighting, a U.S. Air Force weather reconnaissance aircraft had released a dropsonde (a small instrument package dropped from an aircraft to measure atmospheric conditions as it falls) in the approximate area where the pilots later spotted the object. The dropsonde resembled the description given by the pilots, and it reached the ground at 10:15 a.m. However, the Air Force intelligence officer reviewing the case noted a discrepancy: the timing did not match precisely. The dropsonde had already landed before the pilots made contact with their object. Because of this timing problem, the case could not be confirmed as a dropsonde sighting, and it was forwarded for further information.

The Air Force's final evaluation of the case was listed as unknown. The complete case file, comprising eight pages, is reproduced below as held by the National Archives.