William E. Clingerman

William E. Clingerman was an American Air Force officer and engineer who served as a key military monitor in Project Sign, the U.S. Air Force's initial UFO investigation program launched in 1947. As an intelligence officer, he contributed to analyzing early UFO sightings, including the notable 1948 Chiles-Whitted incident involving an Eastern Airlines DC-3. Clingerman, alongside colleagues like Colonel Howard M. McCoy and Captain Sneider, supported the extraterrestrial hypothesis for UFOs, advocating that the objects were likely interplanetary in origin due to the absence of conventional explanations such as domestic or Soviet projects. He participated in efforts to formalize this 'Estimate of the Situation' report, lobbying at the Pentagon, though it was ultimately rejected. Described as a fine engineer, his work helped shape early government UFO research before Project Sign transitioned to Project Grudge.