Public interest in UFOs continued to grow in the 1950s and '60s as the idea of manned spaceflight to other worlds led many people to imagine what—or who—might be traveling the other way. As reports of UFOs proliferated, media coverage seemed to inspire even more reports. Concerned about potential threats to national security, the government began to investigate. Its most notable program, the Air Force's Project Blue Book, began in 1947 and involved the analysis of some 12,600 UFO reports over two decades, most of which were categorized as misidentified natural or man-made objects, such as weather balloons or high-speed aircraft. By the end of 1969, the Air Force declared that none posed a threat or involved an extraterrestrial vehicle. The project's leaders did acknowledge, however, that they could not come up with an explanation for about 700 of the incidents.
That margin of mystery continues to thrill diehard believers around the world, many of whom have organized into groups dedicated to studying UFOs and cataloguing and tracking sightings. The Mutual UFO Network, for example, boasts about 3,000 members in all 50 states and more than a dozen countries. MUFON receives about 500 reports of UFO sightings a month, and some 1,000 volunteers investigate what they see as the most credible ones by interviewing witnesses and collecting photos, radar data, and other evidence.
A big challenge for amateur and professional researchers is the large number of sensational reports that later prove to be hoaxes. In 2009, local television stations reported witness sightings of strange red lights moving through the evening sky around Morristown, N.J., on several days in January and February. As coverage spread nationally, the History Channel series UFO Hunters featured the story. In early April, however, two local men admitted they had created the floating lights by attaching flares to helium balloons, to poke fun at UFO investigators and to demonstrate how unreliable eyewitness accounts are. The mysterious crop circles that have for centuries inexplicably appeared in fields around the world are often held out by some UFO buffs as markings left by alien craft. But skeptics scoff, saying they could easily have been man-made. Such stories frustrate serious researchers. "It really gets hard to separate the wheat from the chaff," acknowledges Bruce Maccabee, a former U.S. Navy research physicist and MUFON state director.
In fact, many scientists and skeptics don't feel that systematically studying UFOs is a valuable endeavor.
"I just don't think the evidence is very good," says Seth Shostak, senior astronomer with the SETI (Search for Extraterrestrial Intelligence) Institute, a research organization based in Mountain View, Calif.
But Kean is convinced that there are enough puzzling cases for officials to give the subject a fresh look. In 1999, she was given a report produced by a group of French military officers, scientists, engineers, and others examining a spate of seemingly unexplained UFO sightings across the world. She was struck by the credibility of the investigators, who concluded there was a need for more careful analysis of these "unknown flying machines" that appeared "guided by a natural or artificial intelligence." The report inspired her to review once-classified government documents and incident reports from several countries (including the United States) as well as relevant photos, radar data, and material from private sources. She also interviewed official UFO investigators for several foreign governments along with military and civilian pilots, some of whom offered firsthand accounts reported in her book.
"These are people that you have to take seriously," Kean says.