# Project Sign

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U.S. Air Force study of UFOs (1948)

Project Sign report

**Project Sign** or **Project Saucer** was an official [U.S. government](/source/U.S._government) study of [unidentified flying objects](/source/Unidentified_flying_object) (UFOs) undertaken by the [United States Air Force](/source/United_States_Air_Force) (USAF) and active for most of 1948. It was the precursor to [Project Grudge](/source/Project_Grudge).

## History

The project was established in 1948 by Air Force General [Nathan Farragut Twining](/source/Nathan_Farragut_Twining), head of the [Air Technical Service Command](/source/Air_Technical_Service_Command), and was initially named Project SAUCER.[1] The goal of the project was to collect, evaluate, and distribute within the government all information relating to UFO sightings, on the premise that they might represent a national security concern.[1]

On April 27, 1949, the U.S. Air Force publicly released a paper prepared by the Intelligence Division of the Air Materiel Command at Wright-Patterson Field, Ohio.[2] The paper stated that while some UFOs appeared to represent actual aircraft, there was not enough data to determine their origin.[3] Almost all cases were explained by ordinary causes, but the report recommended a continuation of the investigation of all sightings.[1][2]

Project Sign was first asserted in the 1956 book *[The Report on Unidentified Flying Objects](/source/The_Report_on_Unidentified_Flying_Objects)* by retired Air Force Captain [Edward J. Ruppelt](/source/Edward_J._Ruppelt) who later directed [Project Blue Book](/source/Project_Blue_Book). In this he also claimed that *Sign* had produced a "[Top Secret](/source/Top_Secret) Estimate of the Situation" which "concluded UFOs were real".[4] No copy of this document or any other corroboration of Ruppelt's claim has been produced, and *[Popular Mechanics](/source/Popular_Mechanics)* called the report "probably more mythological than real".[5] In a Hearing of the [Eighty-ninth Congress](/source/89th_United_States_Congress), Second Session, on January 18, 1966 [L. Mendel Rivers](/source/L._Mendel_Rivers) asserted no such Estimate had ever existed.[6]

Project Sign was followed by Project Grudge after a conclusion was reached that UFO reports could be exploited by a foreign power to induce panic in the population and were therefore a military issue in the post-WW II, [Cold War](/source/Cold_War) climate. This led Project Grudge to conclude (page vi) that UFO reports as the result of "A. Misidentifications of various conventional objects, B. A mild form of mass-hysteria and war nerves, C. Individuals who fabricate such reports to perpetuate a hoax or to seek publicity, and D. Psychopathological persons."[7]

## Caldwell investigation

In May 1949, officers of Project Sign received a letter from an aeronautical company shareholder, who explained that the company had been building aircraft similar to the "flying saucers" which were then a popular topic in the press. This was during the UFO craze following [Kenneth Arnold](/source/Kenneth_Arnold)'s reports of [seeing UFOs](/source/Kenneth_Arnold_unidentified_flying_object_sighting) over [Mount Rainier](/source/Mount_Rainier) and the [Roswell Incident](/source/Roswell_Incident) that followed. The Air Force had canvassed for reports of flying saucers, and the shareholder apparently felt that inventor [Jonathan Edward Caldwell](/source/Jonathan_Edward_Caldwell)'s disk-rotor might explain them.

Tracking down the leads, the team, accompanied by the Maryland Police, visited an abandoned farm in [Glen Burnie, Maryland](/source/Glen_Burnie%2C_Maryland) (outside Baltimore), where the damaged remains of Caldwell's disk-rotor aircraft were discovered. They also tracked down one of the former test pilots of the machine who told them the story of the attempted flight in 1937–8. The team reported that the prototypes could not be responsible for the "flying saucer" reports that were being received from all around the country.[8]

Photographs of the broken disk-rotor machine continue to appear in UFOs books to this day. They were often described as "crashed" flying saucers in earlier works, claiming it was one more example of the USAF being in possession of such vehicles. More recently they are normally connected with the claims that the [Nazis](/source/Nazis) had built working [flying saucers](/source/Flying_saucers) late in the war, lumped together with other disk-shaped aircraft like the [Avrocar](/source/Avrocar), [Sack AS-6](/source/Sack_AS-6) and [Vought V-173](/source/Vought_V-173), in an effort to demonstrate that such aircraft were both possible and well-researched.[9]

## References

1. ^ [***a***](#cite_ref-:0_1-0) [***b***](#cite_ref-:0_1-1) [***c***](#cite_ref-:0_1-2) ["CIA's Role in the Study of UFOs, 1947-90 — Central Intelligence Agency"](https://web.archive.org/web/20070613113822/https://www.cia.gov/library/center-for-the-study-of-intelligence/csi-publications/csi-studies/studies/97unclass/ufo.html). *www.cia.gov*. Archived from [the original](https://www.cia.gov/library/center-for-the-study-of-intelligence/csi-publications/csi-studies/studies/97unclass/ufo.html) on June 13, 2007. Retrieved 2020-04-30.

1. ^ [***a***](#cite_ref-:1_2-0) [***b***](#cite_ref-:1_2-1) Associated Press, Flying Discs Held No Joke, The Oakland Tribune (Oakland, California), April 27, 1949, p. D13.

1. **[^](#cite_ref-Blum1990_3-0)** Blum, Howard, Out There: The Government's Secret Quest for Extraterrestrials. Simon and Schuster, 1990

1. **[^](#cite_ref-Ruppelt_4-0)** Ruppelt, Edward J (1956). [*The Report on Unidentified Flying Objects*](https://archive.org/details/reportonunidenti00rupp/page/n11/mode/2up?q=Estimate+of+the+Situation) (1st ed.). [Doubleday & Company](/source/Doubleday_%26_Company). p. 62. Archived from [the original](https://www.gutenberg.org/cache/epub/17346/pg17346-images.html) on 2010-01-12. Shallet's article - He pointed out how the "furor" about UFO reports got so great that the Air Force was "forced" to investigate the reports reluctantly. He didn't mention that two months after the first UFO report ATIC had asked for Project Sign since they believed that UFO's did exist. Nor did it mention the once Top Secret Estimate of the Situation that also concluded that UFO's were real. In no way did the article reflect the excitement and anxiety of the age of Project Sign when secret conferences preceded and followed every trip to investigate a UFO report. This was the Air Force being "forced" into reluctantly investigating the UFO reports.

1. **[^](#cite_ref-5)** Banias, M. J. (2019-12-17). ["50 Years Ago, the Air Force Tried to Make UFOs Go Away. It Didn't Work"](https://www.popularmechanics.com/military/research/a30257166/project-blue-book-anniversary/). *Popular Mechanics*. Retrieved 2020-05-03.

1. **[^](#cite_ref-6)** ["Unidentified Flying Objects Hearing, Eighty-ninth Congress, Second Session, April 5, 1966"](https://www.google.co.uk/books/edition/Unidentified_Flying_Objects/5tiKlTbhXvMC?hl=en&gbpv=1&dq=alien+interplanetary+aircraft&pg=PA6060&printsec=frontcover). *www.google.co.uk*. United States Congress. House Committee on Armed Services. 1966. p. 6060. Retrieved 4 May 2025.

1. **[^](#cite_ref-7)** ["Project "GRUDGE""](https://upload.wikimedia.org/wikipedia/commons/3/39/Project_GRUDGE_Report_1949.pdf) (PDF). US Government]. Retrieved March 16, 2026.

1. **[^](#cite_ref-8)** Just old contraptions, "Flying Saucers" find proves false alarm, *The Los Angeles Times*, August 21, 1949

1. **[^](#cite_ref-saucers_9-0)** ["An Aeronautical History of Flying Saucers"](https://web.archive.org/web/20101217101425/http://greyfalcon.us/An%20Aeronautical%20History%20of%20Flying%20Saucers.htm). Archived from [the original](http://www.greyfalcon.us/An%20Aeronautical%20History%20of%20Flying%20Saucers.htm) on 2010-12-17. Retrieved 2011-02-11.

## Further reading

- [Dolan, Richard M.](https://en.wikipedia.org/w/index.php?title=Richard_M._Dolan&action=edit&redlink=1) (2002) *UFOs and the National Security State: Chronology of a Cover-up 1941–1973*. [Hampton Roads Publishing Company](/source/Hampton_Roads_Publishing_Company), [ISBN](/source/ISBN_(identifier)) [1-57174-317-0](https://en.wikipedia.org/wiki/Special:BookSources/1-57174-317-0)

- [Peebles, Curtis](/source/Curtis_Peebles) (1994). *Watch the Skies! - A Chronicle of the Flying Saucer Myth*. [Smithsonian](/source/Smithsonian), [ISBN](/source/ISBN_(identifier)) [1-56098-343-4](https://en.wikipedia.org/wiki/Special:BookSources/1-56098-343-4).

## External links

- [the Twining letter](http://www.roswellfiles.com/Articles/twining.htm)

- [Project Sign - Report of February 1949](https://web.archive.org/web/20120227085710/http://www.dod.mil/pubs/foi/homeland_defense/UFOs/2d_af_1.pdf)

Preceded by None US military projects investigating the UFO phenomenon Succeeded by Project Grudge

v t e UFOs Ufology Claimed sightings General List of reported UFO sightings Sightings in outer space Sightings near atomic sites UFO reports and disinformation Pre-20th century Ezekiel's Wheel (circa 622–570 BC) Airship of Clonmacnoise (740s) 1561 celestial phenomenon over Nuremberg 1566 celestial phenomenon over Basel 1665 celestial phenomenon over Stralsund José Bonilla observation (1883) Airship wave (1896–97) Aurora (1897) 20th century Battle of Los Angeles (1942) Ängelholm UFO memorial (1946) Kenneth Arnold (1947) 1947 craze Flight 105 (1947) Roswell (1947) Rhodes (1947) Mantell (1948) Chiles-Whitted (1948) Gorman Dogfight (1948) Mariana (1950) McMinnville photographs (1950) Lubbock Lights (1951) Nash-Fortenberry (1952) Washington, D.C. (1952) Flatwoods monster (1952) Kelly–Hopkinsville (1955) Lakenheath-Bentwaters (1956) Antônio Villas Boas (1957) Levelland (1957) Barney and Betty Hill abduction (1961) Lonnie Zamora incident (1964) Solway Firth Spaceman (1964) Exeter (1965) Kecksburg (1965) Westall (1966) Falcon Lake (1967) Shag Harbour (1967) Pudasjärvi sightings (1967–1971) Jimmy Carter (1969) Finnish Air Force (1969) Pascagoula Abduction (1973) John Lennon UFO incident (1974) Travis Walton incident (1975) Tehran (1976) Petrozavodsk phenomenon (1977) Operação Prato (1977) Zanfretta incident (1978) Valentich disappearance (1978) Kaikoura Lights (1978) Robert Taylor incident (1979) Val Johnson incident (1979) Manises (1979) Cash–Landrum incident (1980) Rendlesham Forest (1980) Trans-en-Provence (1981) Brazilian Night of the UFOs (1986) Japan Air Lines (1986) Ilkley Moor (1987) Voronezh incident (1989) Belgian UFO wave (1989–90) Calvine UFO (1990) Ariel School (1994) Varginha (1996) Phoenix Lights (1997) 21st century USS Nimitz UFO incident (2004) Campeche, Mexico (2004) O'Hare Airport (2006) Alderney (2007) "CARET" Drone Incident (2007) Norway (2009) USS Theodore Roosevelt UFO incidents (2014) Jetpack man (2020–21) High-altitude object events (2023) David Grusch claims (2023) Campo Largo (2026) Confirmed hoaxes Maury Island hoax (1947) Twin Falls, Idaho hoax (1947) Aztec, New Mexico hoax (1949) Southern England (1967) Majestic 12 (1985) Gulf Breeze (1987–88) Alien Autopsy (1995 film) Morristown (2009) Sightings by country Africa (South Africa) Albania Argentina Australia Belarus Belgium Brazil Canada China Czech Republic France Greece India Indonesia Iran Italy Mexico Nepal New Zealand Norway Poland Russia Spain (Canary Islands) Sweden United Kingdom United States Types of UFOs Black triangle Flying saucer Foo fighter Ghost rockets Green fireballs Mystery airship Space jellyfish Types of alleged extraterrestrial beings Energy beings Grey aliens Insectoids Little green men Nordic aliens Reptilian humanoids Studies and timeline Investigation of UFO reports by the United States government The Flying Saucers Are Real (1947–1950) Project Sign (1948) Project Grudge (1949) Flying Saucer Working Party (1950) Project Magnet (1950–1962) Project Second Storey (1952–1954) Project Blue Book (1952–1970) Robertson Panel (1953) Ruppelt report (1956) National Investigations Committee On Aerial Phenomena (1956–1980) Condon Report (1966–1968) Institute 22 (1978–?) Project Condign (1997–2000) Advanced Aerospace Threat Identification Program (2007–2012) Identification studies of UFOs Unidentified Aerial Phenomena Task Force (current) NASA's UAP independent study team Archives of the Impossible Hypotheses Ancient astronauts Cryptoterrestrial Extraterrestrial Interdimensional Psychological perspectives on UFO belief Psychosocial Nazi UFOs Time-traveller Posadist Trotskyism Conspiracy theories Area 51 Storm Area 51 Ashtar Sheran Bob Lazar Dulce Base Men in black Missing scientists Project Serpo Involvement Abduction claims History Narrative Perspectives Insurance Other Implants Cattle mutilation Close encounter Contactee Crop circles Government responses GEIPAN Organizations Ufologists Disclosure movement Culture The Age of Disclosure Fiction Religions list Skepticism List of scientific skeptics Committee for Skeptical Inquiry Government and law United States Congress hearings on UFOs (2022) Unidentified Anomalous Phenomena Disclosure Act (UADPA), USA law (2023) Category

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Adapted from the Wikipedia article [Project Sign](https://en.wikipedia.org/wiki/Project_Sign) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Project_Sign?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.