In November 1953, Captain Charles Hardin was appointed the head of Project Blue Book, and he was replaced by Captain George T. Gregory in 1956. However, most UFO investigations were conducted by the 4602nd Air Intelligence Service Squadron (AISS). Ruppelt wrote that Hardin "thinks that anyone who is even interested (in UFOs) is crazy. They bore him." (Clark, 468). Ruppelt also wrote: "He has been the one big bottleneck in my getting anything from the Air Force because he is afraid that my book will stir things up too much." Jan Aldrich: "Hardin did stop the investigation into an interesting CE2 case in PA by the 4602d. He just ordered it terminated as of no further interest and as explained by reflections in a window. He probably was indeed uninterested in UFOs and was just serving out his time to retirement."