The Chinese spy balloon that was spotted and shot down on Saturday over the coast of South Carolina was far from the first threatening object to trouble American skies. Balloons have dogged U.S. aerial defenses, confounded fighter pilots, and driven UFO sightings for more than 75 years.

Balloons were used for spying and bombing throughout World War I, and German zeppelins regularly crossed the English Channel to drop hand grenades or small bombs on London in early, primitive air raids. One American pilot, Frank Luke, was known as the “Arizona Balloon Buster” for a balloon-shooting spree that downed 14 German balloons across the skies of Europe in just a few weeks in 1918.

But American civilians didn’t begin to be concerned about attacks from the sky until World War II, when major cities instituted blackouts and installed anti-aircraft batteries. Japan lofted about 9,000 balloon bombs toward the West Coast in 1944 and 1945—using the same high-altitude wind currents that aided the Chinese spy balloon. The “Fu-Go” devices carried about 50 pounds of explosives, designed to drop over North America at the end of the flight. The hope was that they would spread fear, ignite forest fires, and bring the war to America’s homeland.

These first intercontinental weapons proved to be more nuisances than aerial terrors; most Americans never even realized the attack was under way, because a press blackout, meant to prevent the Japanese from understanding the effectiveness or direction of their weapons, kept news of the devices silent. Balloons were found across western Canada and many U.S. states, some as far east as Michigan. Although some exploded and startled Westerners, they failed to start any fires. Only one killed people: In May 1945, a woman and a group of children discovered a fallen balloon during a picnic in Oregon and accidentally set it off, which killed her and five others. The devices continued to be found for decades afterward; in 2014, two foresters in British Columbia found a half-buried bomb, the balloon itself long rotted away.

At the end of World War II, the country had escaped unscathed from any aerial assault; the only building damaged in Washington, D.C., was the Lincoln Memorial, which took the brunt of a four-shot burst from an anti-aircraft gun accidentally fired from atop the Interior Department. It was only after the war that the skies became a real threat.

The arrival of the nuclear bomb meant that an entire city could be vaporized by a lone attacker arriving out of the blue sky. As E. B. White wrote in a postwar essay about New York, “The city, for the first time in its long history, is destructible. A single flight of planes no bigger than a wedge of geese can quickly end this island fantasy … All dwellers in cities must live with the stubborn fact of annihilation.”

Coinciding with the dawn of the atomic age was the UFO craze. Reports of a mysterious flight of objects over the Cascades in the Pacific Northwest in 1947 touched off a summer of excited, panicked sightings. UFOs were reported in nearly every state—so many that the Air Force and the newly forming Pentagon began to worry that the Soviet Union had devised some devious new craft.

Six months into the national obsession with UFOs, Captain Thomas F. Mantell, a World War II pilot assigned to the Kentucky Air National Guard, was returning in an F-51 Mustang from a training mission with three other pilots when air-traffic controllers at Godman Army Airfield, in Fort Knox, asked them to investigate a UFO spotted over the state. The white object had been reported by the state police and appeared to be slowly moving over Kentucky at a high altitude. Witnesses estimated that it was 250 to 300 feet in diameter.

About an hour after it came into view, Mantell and two other pilots set off in pursuit. Although his wingman never saw the object, Mantell—a recipient of the Distinguished Flying Cross—radioed that he had the UFO in sight “ahead and above; I’m still climbing.” He had no oxygen equipment aboard and wasn’t meant to fly at such high altitudes, yet Mantell raced ahead of the other fighters into the ever-thinner air, ultimately reaching above 20,000 feet.

His fellow pilots lost sight of him, and an hour later, word came from the state police that his plane had broken apart and crashed into the lawn of a farm near the Tennessee border.

No one knew exactly what he had been chasing. When air-traffic controllers asked him to report on it, he replied with a final message, but by the time investigators arrived at the airbase, no one could remember exactly what he had said. Some recollected him saying, “It appears metallic, of tremendous size,” but others held that his final report was more ambiguous: “It’s above me and I’m gaining on it.”

The death of a fighter pilot chasing a UFO made national headlines. Rumors long circulated (and still do) that Mantell was actually shot down by the UFO. But investigators concluded that he’d flown too high, run out of oxygen, and lost consciousness, and that his plane had broken apart in the high speeds of its fall. The Air Force later theorized that there had been no UFO—that Mantell had been chasing the glowing dot of the planet Venus. But it was hard to imagine how an experienced pilot in the middle of the day could have been fatally confused by a planet.

In 1952, the Air Force’s UFO-investigation program, Project Blue Book, figured out that he’d most likely been chasing a Navy weather balloon. The giant craft, known as Skyhook balloons, were manufactured and launched by General Mills (yes, the cereal company) and used for atmospheric studies. The balloons soared as high as 100,000 feet, and because they were secret at the time, the Air Force observers on the ground wouldn’t have known of their existence. To Mantell, the balloon was literally a UFO: an unidentified flying object.

In the postwar era, balloons represented cutting-edge military technology. The U.S. had multiple secret balloon projects under way—including one, Project Mogul, that is both the official (and the likeliest) explanation for the mysterious wreckage found on a New Mexico ranch near Roswell in 1947. The balloons, once perfected, lofted their way over the Soviet Union—taking photographs, listening, and examining the air for signs of possible nuclear tests—much to the embarrassment and frustration of Soviet officials, who found them out of reach of missiles and fighters.

At home in the U.S., as investigators in the 1940s and 1950s untangled the thousands of UFO sightings of that era, the secret balloons ranked alongside confusion with astronomical phenomena as the most common UFO explanations. Often, after all, the balloons appeared in the sky to people on the ground just as the Chinese balloon did last week: giant, white, slow-moving craft at altitudes where aircraft don’t normally fly.

The threat from the sky has never completely abated. Early in the Cold War, President Harry Truman launched Operation Skywatch and the Ground Observer Corps, a massive civil-defense effort to staff 24-hour watch stations on the lookout for Soviet bombers. President Dwight Eisenhower’s era saw Operation Moonwatch, a similar effort to track satellites post-Sputnik. In later years, the U.S. and Canada formed the North American Aerospace Defense Command with its massive bunker inside Cheyenne Mountain, in Colorado, meant to watch the skies for incoming intercontinental ballistic missiles and, more recently, to track potential space weapons.

Today’s sophisticated surveillance systems seem to have forgotten to protect against a simple balloon. The head of the North American Aerospace Defense Command says that American air defenses and intelligence systems have failed to spot the forays of other Chinese balloons. And thus, on Saturday, the U.S. military deployed one of the most advanced weapon systems in the world, the F-22, to shoot down the modern version of the first aerial weapon the country ever faced.

Notably, the pilot who flew that plane on Saturday is known as FRANK01—a call sign that honors Frank Luke, the balloon-busting ace of 1918.