Project Grudge

American UFO panel

Written by

The Information Architects of Encyclopaedia Britannica

Last updated

July 19, 2026

Quick Summary

Project Grudge was a U.S. Air Force program that investigated unidentified flying object (UFO) sightings from 1949 to early 1950. It was the successor to Project Sign and a precursor to Project Blue Book. Project Grudge collected 244 additional sighting reports. The majority of sightings investigated by these programs were attributed to natural phenomena, human error, hoaxes, or mistaken identification of conventional aircraft. Despite extensive investigations, no physical evidence of extraterrestrial origin was ever collected. The U.S. Air Force's longest-running UFO investigation program, Project Blue Book, ran from 1952 to 1969.123

Summary created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

3 Britannica Sources

Ask Britannica AI about this topic

Britannica doesn't have a full article on this topic, so we've curated a list of our relevant coverage.

unidentified flying object
Flying saucers and Project Blue Book
…Project Sign was succeeded by Project Grudge, which in 1952 was itself replaced by the longest-lived of the official inquiries into UFOs, Project Blue Book, headquartered at Wright-Patterson Air Force Base in Dayton, Ohio. From 1952 to 1969 Project Blue Book compiled reports of 12,618 sightings or events, each of…
Read More
…Project Sign was succeeded by Project Grudge, which in 1952 was itself replaced by the longest-lived of the official inquiries into UFOs, Project Blue Book, headquartered at Wright-Patterson Air Force Base in Dayton, Ohio. From 1952 to 1969 Project Blue Book compiled reports of 12,618 sightings or events, each of…
Read More