Philip Julian Klass was a preeminent American aviation/aerospace journalist and UFO researcher, best known for his skepticism regarding UFOs. In the ufological and skeptical communities, Klass inspires polarized appraisals. He has been called the "Sherlock Holmes of UFOlogy". Klass demonstrated "the crusader's zeal for what seems 'right,' regardless of whether it brings popular acclaim," a trait he claimed his father instilled in him. "I've found," said Klass, "that roughly 97, 98 percent of the people who report seeing UFOs are fundamentally intelligent, honest people who have seen something—usually at night, in darkness—that is unfamiliar, that they cannot explain." The rest, he said, were frauds.

Ufology is the investigation of unidentified flying objects (UFOs) by people who believe that they may be of extraordinary origins. While there are instances of government, private, and fringe science investigations of UFOs, ufology is generally regarded by skeptics and science educators as an example of pseudoscience.