Sources

Where the facts come from

Every factual claim on this site links to its source. This is the full list.

How we checked

Each fact was written in our own words alongside its source. Our build script stores the text of every source and, for each fact, checks that the key words and figures really appear in it. 190 of 190 checks passed when this site was last built (13 November 2026). Where we couldn’t find a named source saying something, we left it out. Where good sources disagree, we say so and give both.

Where sources differ

How fast were Kenneth Arnold’s objects? The Smithsonian says he calculated about 1,200 mph and that some accounts say 1,700 mph. Britannica says he estimated several thousand miles per hour. All agree it was a guess timed between two mountains.
Blue Book’s dates. The 1985 Air Force fact sheet kept by the US National Archives counts 12,618 sightings from 1947 to 1969, which includes the projects before Blue Book. Britannica’s UFO article gives the same total for 1952 to 1969. Same number, different start date.
What the A in UAP stands for. The National Archives says some MoD branches use “unidentified aerial phenomena”. NASA notes that the US Congress changed its own definition from “aerial” to “anomalous” while NASA’s study was under way. Both are in use.
Rendlesham. Nick Pope and two of the airmen call it the best-documented UFO incident ever. Sceptical investigators point to a fireball, a lighthouse and bright stars. Halt’s memo is real, and the MoD’s own records from the time show no unusual radar returns. We give both sides and let the records speak.
The Navy videos. The US Defense Department still lists what the videos show as “unidentified”. NASA’s study team analysed one, GoFast, and found the object was most likely drifting with the wind. “Unidentified” and “explained” can both be fair at once: one is an official label, the other a careful best guess.

How we checked

Where sources differ

All sources (32)