Sewart AFB, Nashville, Tenn., May 1961May 1961

On May 27, 1961, a triangular-shaped object appeared near Nashville, Tennessee, at very high altitude. The sighting occurred during daylight hours. Some witnesses reported the object resembled a large delta-wing aircraft, while an amateur astronomer who viewed it through a telescope said it looked like a pyramid with a cable and instrument package dangling beneath it. Military jets from Memphis Naval Air Station were scrambled and reached 47,000 feet, but the object appeared to be at 60,000 feet or higher, beyond their reach. A reporter from the Nashville Tennessean photographed the object.

The case generated considerable public discussion and letters of inquiry to the Air Force. One correspondent asked officials to explain how such an object could travel from Memphis to Nashville in two hours when weather reports showed wind speeds above 50,000 feet were only 5 to 15 knots. The Strategic Air Defense Command in Colorado Springs claimed to have no record of anything in the area at that time.

The Air Force investigated through its technical intelligence center and concluded the object was most likely a weather balloon, probably one launched from Berry Field (now Nashville International Airport) about 30 minutes before the sighting. A local television station employee had observed the object through a telescope and identified it as a balloon with a box attached to it by a cable. Two Navy pilots who saw it aloft also judged it to be a balloon. At sunset, the object passed into the earth's shadow and became invisible. The Air Force noted that weather balloons at extreme altitude can appear extremely bright, metallic, and may look larger than they actually are due to reflected sunlight and the angle of observation.

A subsequent Air Force response acknowledged some discrepancies in the wind-speed analysis and requested precise position reports with azimuth and altitude measurements. The officer explaining the conclusion noted that weather balloons reach altitudes of 50,000 feet or higher, and that the movements of such balloons can be misleading without exact measurements from known locations. He also clarified that various sizes and configurations of balloons are launched daily from over 100 locations across the United States, and described the appearance of radiosondes (instruments suspended beneath balloons to measure atmospheric conditions) as potentially unusual due to their trailing parachutes and sensor packages. The Air Force evaluation listed in the case metadata is "unknown," though the technical analysis points toward a balloon explanation.

The full case file is reproduced below as held by the National Archives, comprising 12 pages.