Type: Government Report
Source: United States Air Force - Project Sign
The 1948 Project Sign Estimate of the Situation was an internal United States Air Force report examining unexplained aerial phenomena reported during the early years of UFO investigations. The report reportedly concluded that some UFO cases were difficult to explain through conventional means and may have involved extraterrestrial technology. The document was later rejected by Air Force leadership and is considered one of the most significant early government UFO investigation records.