The study of the group of phenomena classed as unidentified flying objects (UFOs). The idea that strange objects seen in the sky might be a significant phenomenon for study arose out of the flying-saucer craze that began in 1947. Most cases could be explained away as misperceptions of natural objects or frauds, but those who took the phenomena seriously maintained that a small proportion of cases could not be dismissed so easily. The study raises questions about how best to use nonexpert testimony about transient phenomena. In a popular culture that seeks to link the phenomena to extraterrestrial visitors, such a study can readily be made to look disreputable.
The study of the evidence for, and of explanations of, these observations ufology has generated a huge mass of literature, and organizations have been founded in several countries to foster such studies, for example the United States J. Allen Hynek Center For UFO Studies and the British UFO Society.