[ILLEGIBLE], [ILLEGIBLE] - Incident Number: 181Date unknown

On the night of October 15, 1948, a U.S. Air Force F-61 night fighter aircraft operating northwest of Fukuoka, Japan made repeated radar and visual contact with an unidentified aircraft. The pilot, 1st Lt. Oliver Hemphill Jr., and radar observer, 2nd Lt. Barton Halter, attempted six interceptions over approximately twelve minutes.

The object first appeared on radar about nine miles ahead, traveling at roughly 200 mph. As the F-61 closed in, the target suddenly accelerated and descended at a rate the pilots found impossible to match. It maneuvered beneath their aircraft and disappeared from both radar and visual sight. The sequence repeated five more times. In the third encounter, Hemphill caught a visual silhouette against the moonlit undercast. He described it as roughly 20 to 30 feet long with a rounded nose, stubby fuselage, and a sharp cutoff at the rear. He ruled out known jet aircraft like the Me-262, comparing it instead to the German Me-163 rocket fighter. The object showed a high rate of acceleration and seemed aware of the F-61's position at all times, which raised the possibility it carried radar warning equipment.

Ground radar at the site never detected the target, picking up only the F-61 itself. Weather conditions in the area were good with unlimited ceiling and five to six miles of visibility. An Air Force evaluation noted one apparent discrepancy: ground radar should have detected the object if the airborne radar contact was genuine. The file states there is no astronomical explanation evident, and the exact nature of what the pilots encountered remains unexplained.

The complete case file as held by the National Archives is reproduced below across 35 pages.