Estimate of the Situation –
Project Sign was first asserted in the 1956 book The Report on Unidentified Flying Objects by retired Air Force Captain Edward J. Ruppelt who later directed Project Blue Book. In this he also claimed that Sign had produced an “Estimate of the Situation” which endorsed an interplanetary explanation for UFOs, but General Hoyt Vandenberg, Chief of Staff of the Air Force, shut down Project Sign for lack of proof.[4] No copy of this document or any other corroboration of Ruppelt’s claim has been produced, and Popular Mechanics called the report “probably more mythological than real”.[5]