UFO or UAP? What the letters mean
Unidentified, not necessarily alien.
How this site works. Every fact is in our own words with its source linked beside it. The pictures are our own drawings. We never say aliens have been found, because nobody has shown that they have; we show what was reported, then what the evidence says.
UFO is short for “unidentified flying object”, a term that came from the US Air Force. The National Archives
To the military, a UFO means something in the sky that can be seen but not recognised. It does not mean something from another world. The National Archives
Britannica defines a UFO as any object or light in the sky that the person watching can’t readily identify. Britannica
From UFO to UAP
Some branches of the UK Ministry of Defence prefer the term UAP, for “unidentified aerial phenomena”. The National Archives
The US Defense Department calls UAP a new term for what used to be called unidentified flying objects. US Defense Dept, 2024
When NASA’s UAP study began, the US Congress defined UAP as “unidentified aerial phenomena”. During the study, the term was changed to “unidentified anomalous phenomena”. NASA UAP study
NASA describes UAP as observations of events in the sky that can’t be identified as aircraft or known natural phenomena. NASA Science
Aerial or anomalous?
Some branches of the UK Ministry of Defence prefer the term UAP, for “unidentified aerial phenomena”. The National Archives
When NASA’s UAP study began, the US Congress defined UAP as “unidentified aerial phenomena”. During the study, the term was changed to “unidentified anomalous phenomena”. NASA UAP study
Both versions are still in use. They mean much the same thing to you and me: something seen that nobody could identify.
Why things stay “unidentified”
AARO, the US government’s UAP office, says many cases are labelled “unidentified” simply because the sensors didn’t collect enough information to say what they were. AARO FAQ
AARO says no single explanation covers most UAP reports. AARO FAQ
The unidentified cases included ones where there wasn’t enough information to match a known cause. Britannica
Who keeps the records?
In the UK, official reporting and recording of UFO sightings began in the early 1950s. The National Archives
Until 1967 the Ministry of Defence destroyed its UFO files every five years, so many early records are lost. The National Archives
Since 1970, most surviving MoD UFO files have been reviewed for release at The National Archives, because so many people are interested. The National Archives
Blue Book’s declassified records have been at the US National Archives in Washington, D.C., since 1976, open to the public. Britannica, Blue Book
Our view: “unidentified” is an honest word. It means “we don’t know yet”, and that is where all good science starts. It is not a polite code for “alien”.