The year 1947 is often marked as the beginning of our fascination with flying saucers and unidentified flying object (UFO) sightings. That is mostly because of two specific events, one seen from the air and the other on the ground.

On June 24th of that year, Kenneth Arnold was flying his small plane across Washington State. It was a bright, clear day as Arnold described it. He was on his way to an air show in Oregon, but decided to do some exploring around Mount Rainier. The mountain was near a recent military plane disappearance, presumed crashed. A reward was being offered to anyone able to find the site of the crash.

In the cockpit, Arnold saw a DC-4 aircraft flying about 15 miles away. Then he noticed something else. According to Arnold, a bright flash reflected light into his airplane. Looking around for the source of the reflection, Arnold spotted a group of nine objects flying close to Mount Rainier. They were all flying in the same formation, similar to a flock of geese, as Arnold described it.

Arnold also described the objects as large in size, no tail, and traveling very fast at speeds estimated up to 1,700 mph. They were also round in shape, something Arnold had never seen before as an experienced pilot. Flying perilously close to the mountain range, they were “saucer-like disks,” he said.

At first, he guessed that what he might be seeing were advanced military aircraft being tested. However, Arnold commented at the time, “The more I observed these objects, the more upset I became, as I am accustomed and familiar with most all objects flying whether I am close to the ground or at higher altitudes.”

After a few minutes of observation, the objects disappeared from Arnold’s view. After landing his plane, Arnold recounted what he saw, and the news spread quickly. The era of the alien flying saucer was born.

But what did Arnold actually see that clear day? A brief U.S. air force investigation concluded that the pilot had seen some sort of mirage, perhaps involving unusual looking clouds. Some people just thought Arnold was crazy. Almost immediately after the incident, people started reporting their own “saucer” sightings.

After his famous flight, Kenneth Arnold bought a camera and kept it with him whenever he flew. He was determined to prove in photos what he saw that June day in 1947. However, he never reported seeing anything out of the ordinary again.

Less than a month after Arnold’s UFO sighting, on July 7, a rancher named Mac Brazel found strange debris lying around his property near Roswell, New Mexico. What he discovered were described as metallic sticks, as well as plastic and paper-like chunks of material. Brazel called the sheriff of Roswell. Then officials from the local army base were summoned to the ranch.

Initially, the Roswell Army Air Field issued a press release stating that a “flying disk” had crashed on Brazel’s ranch during a powerful storm. Just a few hours later, scientists who said they saw some of the material from the site insisted that it was remnants from a weather balloon.

The downed weather balloon was being used as part of an experiment named Project Mogul, according to authorities. Project Mogul was designed to use heavy-duty weather balloons to reach the upper atmosphere. The goal was to detect sound waves from Soviet nuclear tests during the early years of the Cold War. Being a secretive project, however, led skeptics to conclude that it was all part of an elaborate government cover-up.

The skepticism only increased in the 1950s, when the Air Force conducted a series of secret “dummy drops” in New Mexico. Using crash-test dummies, they dropped the featureless human looking objects over various fields to test ways pilots survive falls from high altitudes. The dummies were then retrieved by army personnel for analysis.

To some residents already suspicious of the earlier Roswell incident, it certainly seemed like extraterrestrial beings were falling out of the sky. The alleged crash victims were then suspected of being scooped up and experimented on.

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In 1994, the Pentagon declassified its files on Project Mogul and the dummy drops; it also published a report debunking the rumored extraterrestrial incidents around Roswell. However, that hasn’t put a stop to ongoing suspicion of government cover-ups, as well as annual pilgrimages to the Roswell area by people seeking what for them is the real story.