One of the foremost and most forceful critics of Ufology. He graduated from Iowa State University in electrical engineering, worked during World War II as an aircraft electronic engineer for General Electric, and then for many years was editor of Aviation Week (subsequently Aviation Week and Space Technology).
In the mid-1960s, he began to investigate the reports of flying saucers and UFOs. Klass was soon convinced that they could be explained as hoaxes, publicity stunts, optical illusions, or possibly as electric discharges akin to Ball Lightning in places where the electric field was exceptionally high (a theory later shown to be scientifically unsound). In succeeding years, Klass became the scourge of the ufologists, writing several books—UFOs— Identified (1968), UFOs Explained, and UFOs—The Public Deceived (1983)—and publishing the Skeptics UFO Newsletter. He appeared on talk shows attacking UFO claims. He became associated with Paul Kurtz, editor of the Humanist, and several other skeptics in the committee for the scientific investigation of claims of the paranormal (CSICOP). In the 1980s, he investigated claims of alien abductions and published UFO Abductions: A Dangerous Game (1989). Klass attributed these highly dramatic accounts of abduction, rape, dissection, and so on to hoaxes, fantasies, and in particular to false memory syndrome, since he thought memories elicited under hypnosis were a mixture of fantasy, recalled dreams, dim memories of science fiction, and suggestions by the hypnotist.