A flying saucer, or flying disc, is a purported type of disc-shaped unidentified flying object (UFO). The term was coined in 1947 by the United States (US) news media for the objects pilot Kenneth Arnold claimed flew alongside his airplane above Washington State. Newspapers reported Arnold's story with speed estimates implausible for aircraft of the period. The story preceded a wave of hundreds of sightings across the United States, including the Roswell incident and the Flight 105 UFO sighting. A National Guard pilot died in pursuit of a flying saucer in 1948, and civilian research groups and conspiracy theories developed around the topic. The concept quickly spread to other countries. Early reports speculated about secret military technology, but flying saucers became synonymous with aliens by 1950. The more general military terms unidentified flying object (UFO) and unidentified anomalous phenomena (UAP) have gradually replaced the term over time.