UFO (Unidentified Flying Object)

"UFO" stands for Unidentified Flying Object: any aerial object, light, or craft that the observer — and, often, subsequent investigation — fails to identify. USAF Captain Edward J. Ruppelt, head of Project Blue Book, coined the term around 1952 to replace "flying saucer," the 1947 press label he considered too narrow, since it presupposed a disc shape when witnesses actually reported cigars, triangles, lights and spheres too. The distinction is the whole point of the word: "unidentified" describes a gap in the observer's or investigator's knowledge, not a claim about extraterrestrial origin. Roughly 90-95% of investigated reports resolve to conventional causes — aircraft, Venus, balloons, satellites — once enough data comes in; the residual unresolved fraction is what keeps the term alive, and the case that made "UFO" a household word is Kenneth Arnold's 1947 sighting near Mount Rainier, which predates the acronym itself. Skeptics use "UFO" to flag a temporary evidence gap awaiting a mundane answer; believers use it as shorthand for the whole open question of anomalous aerial phenomena. Since 2022 the U.S. government has favored "UAP" instead, but "UFO" remains the public's default word for the mystery.