How the U.S. Air Force Investigated UFOs During the Cold War

On the afternoon of June 24, 1947, amateur aviator Kenneth Arnold was flying near Mt. Rainier, Washington, when he suddenly spotted nine unusual objects on the horizon. Arnold claimed the craft flitted from side to side and flipped in unison like “the tail of a Chinese kite,” and he estimated they were moving at around 1,700 miles per hour—far faster than any known aircraft. He initially assumed the physics-defying objects must be secret military vehicles, but he later admitted the incident was “as much a mystery to me as it is to everybody else.” Arnold’s extraordinary story soon found its way into newspapers across the country, and reporters pounced on his description of the objects as moving “like a saucer if you skip it across water.” Within days, the term “flying saucer” was born.

Coupled with the famed July 1947 incident at Roswell, New Mexico, when the Air Force claimed a military weather balloon was mistaken for an alien spacecraft, Arnold’s encounter helped spark a wave of “flying saucer” sightings across the United States. The military brushed aside most of these “close encounters” as misidentifications or mere hokum, but a few reports came from air-traffic controllers and commercial pilots—people trained to search the skies with a discerning eye. The hysteria also dovetailed with the beginning of the Cold War, leading many to speculate that the mysterious sightings might be hostile Soviet aircraft.Thus began official government investigations into the mysterious phenomena.Following an official Air Force inquiry, Lt. General Nathan Twining fired off a memo in late-1947 describing the “flying disc” phenomenon as “something real and not visionary or fictitious.” He suggested the military launch an investigation into the source of the sightings. By 1948, the Air Force had initiated “Project Sign,” the first of three military offices tasked with collecting and analyzing reports of what were termed “Unidentified Flying Objects.” Project Sign’s investigators quickly concluded that UFOs weren’t coming from behind the Iron Curtain—their flight characteristics simply didn’t match those of any manmade aircraft—but some on the team may have embraced the idea that UFOs were not of this world. 

According to Air Force officer Edward Ruppelt and others who studied UFOs for the government, Project Sign produced a report in the summer of 1948 speculating that the sightings might be evidence of “interplanetary” or extraterrestrial craft. Air Force brass supposedly rejected and destroyed the document on the grounds that there was no hard evidence for its conclusions. To this day, no copies of the report have ever been recovered.Project Sign was terminated in late 1948 and replaced by the short-lived Project Grudge, which was later succeeded in 1951 by the now-famous Project Blue Book. Based at Wright-Patterson Air Force Base near Dayton, Ohio, Blue Book served as the government’s main repository for sightings of unidentified aerial phenomena. Over the next 18 years, its tiny staff investigated thousands of reports and often went into the field to interview Americans who had experienced close encounters with all manner of flying saucers and discs, cigar-shaped rockets and dazzling nighttime lights.The “Blue Book” era began with a bang. Projects Sign and Grudge had only averaged around 170 UFO reports each year, but 1952 brought an unprecedented 1,501 sightings. 

Perhaps the most extraordinary of all came in July 1952, when a series of unusual blips suddenly lit up radar screens across Washington, D.C. Bewildered military personnel scrambled jets to intercept the bogies, but while their pilots reported seeing bright lights dancing through the night sky, they were unable to catch them. In the wake of the sightings, the U.S. Air Force held a press conference in which Major General John Samford said the government would continue to investigate reports made by “credible observers of relatively incredible things.” Samford said the events in Washington may have been “temperature inversions”—layers of warm air that can cause radar aberrations—and he assured Americans that UFOs did not bear “any conceivable threat to the United States.”

Allen Hynek (Credit: David Cupp/The Denver Post via Getty Images)