Vallée is also an important figure in ufology, pioneering along with J. Allen Hynek, the scientific study of the UFO phenomenon, authoring several books, and creating along with his wife Janine, the first computer database of UFO sightings. As his involvement in ufology evolved, he began favoring the Interdimensional Hypothesis, a view that was not well received by the ufology community at-large. When screenwriter and producer Steven Spielberg was working on the film Close Encounters of the Third Kind, Vallée proposed to him that UFOs would be even more interesting if they were not portrayed simply as space ships. Although Spielberg tended to agree, he felt that such a portrayal would fail to deliver on what the audience was expecting and consequently jeopardize the film's Hollywood success. However he did model the character of Claude Lacombe ( played by François Roland Truffaut ) after Vallée.
Vallée first became interested in UFOs during May 1955 when he and his mother observed a slivery domed disk hovering about 1000 feet up over their home Pontoise. A fellow student who lived about a mile away also had time to view the disk through binoculars, and his account matched Vallée's. Then During 1961 while employed as an astronomer at the Paris Observatory. One of his first assignments was tracking satellites, during which time he and his associates began noticing objects that Vallée described as "not satellites" and "fairly elusive". One night they tracked a very bright object in retrograde orbit. This was at a point in aerospace history when launching a satellite into retrograde orbit was thought to be beyond Earth technology. The day after their sighting, the data from the anomalous observation was confiscated and erased.
Vallée subsequently formed a small network of scientists who were interested in UFOs and learned that data was routinely suppressed to avoid ridicule. Over the years he has been approached in confidence by highly placed civilian and military people who have had their own UFO sightings. Vallée remains open minded but scientifically skeptical regarding the UFO phenomenon, and tends to be critical of contactees, cults, and the use of hypnosis as an information gathering tool.
Skeptics may want to note that Vallée's 1961 sighting may have an explanation in terrestrial science. During the late 1950s and early 1960s, the Russians, built and tested the Vostok launch vehicle, an efficient and powerful rocket that among other things, was used to place maneuverable reconnaissance satellites into Earth orbit. The Vostok name was classified until April 1961 when Yuri Alekseyevich Gagarin made world news by becoming the first man in space. So Vallée would not have known about any secret Russian launches around the time of his sighting. This is not to say that what Vallée saw was a secret Russian device, only that unless Vallée's sightings included the classic UFO maneuvers that still can not be duplicated by 21st century human engineering, that secret Russian Vostok launches are a reasonable and plausible explanation.