Incident #135 Sighting Report — Rapid City, South Dakota, August 1947

This document details Incident #135, a sighting reported by an Air Force officer occurring between August 15 and August 20, 1947, near Rapid City Air Force Base in South Dakota. The witness reported observing approximately twelve 'flying discs' at a distance of four miles. The objects were described as elliptical, brilliant yellowish-white, and approximately 100 feet in size. They were observed in a tight diamond formation, moving from the northwest to the southwest at an estimated speed of over 500 mph. The objects descended from an altitude range of 5,000 to 10,000 feet down to 6,000 feet. The witness noted that the objects were highly maneuverable, maintained equal spacing during all maneuvers, and produced no sound or exhaust trails. The observation lasted for approximately one minute. The official evaluation, which includes input from Dr. Hynek, notes that while the reporter is considered a reliable observer, the report contains limitations common to such sightings. Specifically, the document highlights that distance cannot be accurately estimated without prior knowledge of an object's size, which in turn renders speed and size estimates unreliable. Furthermore, the report notes that the witness did not remember the exact date of the observation, which was reported a year later. Dr. Hynek suggested that the phenomenon might be explained by detached auroral streamers, noting that the night was very dark and the moon was new, providing favorable conditions for such observations. The incident is categorized within the Project Grudge files as an unexplained event, though it is noted that the description provided offers no clear astronomical explanation.