Project Grudge

UFO sightings were explained as conventional aircraft, balloons, stars, planets, meteors, optical illusions, solar reflections, or even "large hailstones."

The report's conclusions included: The "Recommendations" section suggested that Air Force personnel receive basic instruction in astronomical phenomena.

An article by Sidney Shallet appeared in two consecutive issues of the Saturday Evening Post (April 30 and May 7, 1949) and supported Project Grudge's assessment that UFO reports could be explained by mundane phenomena, and that hoaxes and crackpots played a prominent role in popularizing UFOs.

Project Grudge also received criticism from former intelligence officer Edward J. Ruppelt, who was "convinced of the alien nature of UFOs and how he has seen the military and the U.S. government trying to discredit the extraterrestrial hypothesis".

Both Hynek and Ruppelt claimed that Project Grudge was "as far from an objective, scientific examination of the phenomenon as one could get".