Ruppelt was the first head of the project. He was an experienced airman, having been decorated for his efforts with the Army Air Corps during World War II, and having afterward earned an aeronautics degree. He officially coined the term "Unidentified Flying Object", to replace the many terms ("flying saucer", "flying disk" and so on) the military had previously used; Ruppelt thought that "unidentified flying object" was a more neutral and accurate term. Ruppelt resigned from the Air Force some years later, and wrote the book "The Report on Unidentified Flying Objects", which described the study of UFOs by United States Air Force from 1947 to 1955. American scientist Michael D. Swords wrote that "Ruppelt would lead the last genuine effort to analyze UFOs".