This document provides background information on UFO sightings throughout history. It discusses early sightings in the 1940s and the coining of the term "flying saucer" in 1947. It then outlines several famous UFO sightings and cases from the 1940s to 2000s, including the Roswell incident, Betty and Barney Hill abduction, Phoenix Lights, and Mexican military footage. It also summarizes the conclusions of Project Blue Book that UFOs do not represent a threat or advanced technology beyond our understanding. The document gives an overview of the history of UFO sightings and cases through prominent examples.