Project 10073 Record: Incident #17 - Mt. Rainier, Washington, 24 June 1947

This document compiles reports and evaluations regarding the sighting of nine unidentified objects by pilot Kenneth Arnold on June 24, 1947, near Mt. Rainier, Washington. Arnold, a businessman and private pilot, reported observing a chain of nine circular, mirror-like objects flying in a diagonal formation from north to south at approximately 9,500 feet. He estimated their speed at over 1,600 miles per hour and noted they lacked tails. Arnold's account, which he later sold to Fate magazine, triggered widespread media attention and a surge in similar reports across the United States. The Air Force, specifically through the evaluation of Dr. J. Allen Hynek and the Air Material Command, concluded that the sighting was likely a mirage caused by atmospheric inversions. Investigators highlighted significant inconsistencies in Arnold's data, particularly regarding the relationship between his estimated distance, size, and speed of the objects. Internal Air Force correspondence suggests that the publicity surrounding the incident was largely responsible for subsequent reports. The file includes various documents, including internal memos, teletype messages, and statements from Arnold, as well as a later analysis by Dr. Hynek that dismisses the sighting as scientifically inconsistent and likely a misidentification of known phenomena or aircraft under specific atmospheric conditions.