In response to numerous reports of "flying saucers", the
United States Air Force established
Project Sign in 1948 to examine sightings of unidentified flying objects. Hynek was contacted to act as a scientific consultant to Project Sign. He studied UFO reports and decided whether the phenomena described therein suggested known
astronomical objects.
When Project Sign hired Hynek, he was skeptical of UFO reports. Hynek suspected that they were made by unreliable witnesses, or by persons who had misidentified man-made or natural objects.
In 1948, Hynek said that "the whole subject seems utterly ridiculous," and described it as a fad that would soon pass."
In his 1977 book, Hynek said that he enjoyed his role as a debunker for the Air Force. He also said that debunking was what the Air Force expected of him.
In April 1953, Hynek wrote a report for the
Journal of the Optical Society of America titled "Unusual Aerial Phenomena," which contained one of his best-known statements:
"Ridicule is not part of the scientific method, and people should not be taught that it is. The steady flow of reports, often made in concert by reliable observers, raises questions of scientific obligation and responsibility. Is there ... any residue that is worthy of scientific attention? Or, if there isn't, does not an obligation exist to say so to the public—not in words of open ridicule but seriously, to keep faith with the trust the public places in science and scientists?"
In 1953, Hynek was an associate member of the
Robertson Panel, which concluded that there was nothing anomalous about UFOs, and that a
public relations campaign should be undertaken to debunk the subject and reduce public interest. Hynek would later lament that the Robertson Panel had helped make UFOs a disreputable field of study.
As UFO reports continued to be made, some of the testimonies, especially by military pilots and police officers, were deeply puzzling to Hynek. He once said, "As a scientist I must be mindful of the lessons of the past; all too often it has happened that matters of great value to science were overlooked because the new phenomenon did not fit the accepted scientific outlook of the time."
In a 1985 interview, when asked what caused his change of opinion, Hynek responded, "Two things, really. One was the completely negative and unyielding attitude of the Air Force. They wouldn't give UFOs the chance of existing, even if they were flying up and down the street in broad daylight. Everything had to have an explanation. I began to resent that, even though I basically felt the same way, because I still thought they weren't going about it in the right way. You can't assume that everything is black no matter what. Secondly, the caliber of the witnesses began to trouble me. Quite a few instances were reported by military pilots, for example, and I knew them to be fairly well-trained, so this is when I first began to think that, well, maybe there was something to all this."
Hynek remained with Project Sign after it became
Project Grudge (though he was far less involved in Grudge than he had been in Sign). Project Grudge was replaced with
Project Blue Book in early 1952, and Hynek remained as scientific consultant. Air Force Captain
Edward J. Ruppelt, Blue Book's first director, held Hynek in high regard: "Dr. Hynek was one of the most impressive scientists I met while working on the UFO project, and I met a good many. He didn't do two things that some of them did: give you the answer before he knew the question; or immediately begin to expound on his accomplishments in the field of science."
Though Hynek thought Ruppelt was a capable director who steered Project Blue Book in the right direction, Ruppelt headed Blue Book for only a few years.
Hynek has also stated his opinion that after Ruppelt's departure, Project Blue Book was little more than a public relations exercise, further noting that little or no research was undertaken using the scientific method.