On June 24, 1947, private pilot Kenneth Arnold saw what he described as a string of nine shiny unidentified flying objects flying past Mount Rainier at speeds that he estimated to be at least .

This was the first post-World War II sighting in the United States that garnered nationwide news coverage and is credited with being the first of the modern era of UFO sightings, including numerous reported sightings over the next two to three weeks. Arnold's description of the objects also led to the press quickly coining the terms flying saucer and flying disc as popular descriptive terms for UFOs.

Sighting

On June 24, 1947, Arnold was flying from Chehalis, Washington, to Yakima, Washington, in a CallAir A-2 on a business trip. He made a brief detour after learning of a $5,000 reward (equivalent to $ today) for the discovery of a U.S. Marine Corps C-46 transport airplane that had crashed near Mount Rainier. The skies were completely clear and there was a mild wind.Garber, Megan (June 15, 2014). "The Man Who Introduced the World to Flying Saucers". The Atlantic. Retrieved October 30, 2021.

A few minutes before 3:00 p.m. (15:00) at about in altitude and near Mineral, Washington, Arnold had given up his search for the downed airplane and began heading eastward towards Yakima, when he noticed a bright flashing light, similar to sunlight reflecting from a mirror. Worried that he might be dangerously close to another aircraft, Arnold scanned the skies around him but all he could detect was a DC-4 to his left and behind him, about away, with the assistance of ground radar.

About 30 seconds after seeing the first flash of light, Arnold saw a series of bright flashes in the distance off to his left, or north of Mount Rainier, which was then around away. He thought the reflections might be sunlight on his airplane's windows, but a few quick tests (rocking his airplane from side to side, removing his eyeglasses, later rolling down his side window) ruled this out. The reflections came from nine objects, flying in a long chain. For a moment, Arnold thought that they might be a flock of geese, but quickly ruled this out for a number of reasons, including the altitude, bright glint, and obviously very fast speed. He then thought they might be a new type of jet and started looking intently for wings and other appendages, but was surprised to not see any.Lacitis, Erik (June 24, 2017). "‘Flying saucers’ became a thing 70 years ago Saturday with sighting near Mount Rainier". The Seattle Times. Retrieved October 30, 2021.

The objects quickly approached Mount Rainier and then passed in front of it, usually appearing darker in profile against the bright white snowfield covering the peak, but occasionally still giving off bright light flashes as they flipped around erratically. Arnold reported at times the objects appeared so thin and flat, they were practically invisible. According to Jerome Clark, Arnold described them as a series of objects with convex shapes, though he later revealed that one of the objects differed from the other eight by being crescent-shaped. Several years later, Arnold would state he likened their movement to saucers skipping on water, without comparing their actual shapes to saucers, but initial quotes from him do indeed have him comparing their shape to a "saucer", "disc", "pie pan", or "half moon", or generally convex and thin.

Using a Dzus cowling fastener as a gauge to compare the nine objects to the distant DC-4, Arnold estimated their angular size as slightly smaller than the DC-4, about the width between the outer engines (about ). Arnold also said he realized that the objects would have to be quite large to see any details at that distance and later, after comparing notes with a United Airlines crew that had a similar sighting 10 days later (see below), placed the absolute size as larger than a DC-4 airliner (or greater than in length). Army Air Force analysts would later estimate 140 to , based on analysis of human visual acuity and other sighting details (such as estimated distance).

Arnold said the objects were grouped together, as Ted BloecherThe UFO Wave of 1947 by Ted Bloecher, 1967; URL accessed March 7, 2007 writes, "in a diagonally stepped-down, echelon formation, stretched out over a distance that he later calculated to be five miles". Though they were moving on a more or less level horizontal plane, Arnold said the objects weaved from side to side ("like the tail of a Chinese kite" as he later stated), darting through the valleys and around the smaller mountain peaks. They would occasionally flip or bank on their edges in unison as they turned or maneuvered causing almost blindingly bright or mirror-like flashes of light. The encounter gave him an "eerie feeling", but Arnold suspected he had seen test flights of a new U.S. military aircraft.

As the objects passed Mount Rainier, Arnold turned his plane southward on a more or less parallel course. It was at this point that he opened his side window and began observing the objects unobstructed by any glass that might have produced reflections. According to Arnold, the objects did not disappear and continued to move very rapidly southward, continuously moving forward of his position. Curious about their speed, he began to time their rate of passage: he said they moved from Mount Rainier to Mount Adams where they faded from view, a distance of around , in one minute and forty-two seconds, according to the clock on his instrument panel. When he later had time to do the calculation, the speed was over . This was about three times faster than any manned aircraft in 1947. Not knowing exactly the distance where the objects faded from view, Arnold conservatively and arbitrarily rounded this down to an hour, still faster than any known aircraft, which had yet to break the sound barrier.

Arnold shares the story After landing in Yakima, Arnold described what he had seen to a number of pilot friends, who suggested that maybe he had seen guided missiles or a new airplane being secretly developed by the United States Army.Spokane (Washington) Daily Chronicle, p. 1 Arnold refueled his airplane and continued on his way to an air show in Pendleton, Oregon. He was first interviewed by reporters the next day (June 25), when he went to the office of the East Oregonian in Pendleton.Lagrange, Pierre (1988), « “ It Seems Impossible, but There It Is ” », in John Spencer & Hilary Evans (eds.), Phenomenon: From Flying Saucers to UFOs – Forty Years of Facts and Research. London: Futura Publications, 1988, pp. 26–45. Reporters assessed Arnold as highly-credible when they interviewed him at length;Lagrange, Pierre (1998), « A Moment in History: An Interview with Bill Bequette », International UFO Reporter, Vol. 23, n° 4, Winter, pp. 15, 20 as historian Mike Dash wrote:Dash, Mike, Borderlands: The Ultimate Exploration of the Unknown; Woodstock: Overlook Press, 2000;

Speaking to a reporter for the Associated Press, Arnold told him: "This whole thing has gotten out of hand. I want to talk to the FBI or someone. Half the people look at me as a combination of Einstein, Flash Gordon and screwball. I wonder what my wife back in Idaho thinks."Spokane (Washington) Daily Chronicle, p. 1 , Eugene (Oregon) Register-Guard, June 27, 1947, p. 1 ; Bremerton (Washington) Sun, June 28, 1947, p. 1

Corroboration

On July 4, 1947, the Oregon Journal in Portland, Oregon reported receiving a letter from an L. G. Bernier of Richland, Washington (about east of Mount Adams and southeast of Mount Rainier). Bernier wrote that he saw three of the strange objects over Richland flying "almost edgewise" toward Mount Rainier about one half-hour before Arnold. Bernier thought the three were part of a larger formation. He indicated they were traveling at high speed: "I have seen a P-38 appear seemingly on one horizon and then gone to the opposite horizon in no time at all, but these disks certainly were traveling faster than any P-38. [Maximum speed of a P-38 was about 440 miles an hour.] No doubt Mr. Arnold saw them just a few minutes or seconds later, according to their speed."Oregon Journal, Portland, July 4, 1947, p. 2 The previous day, Bernier had also spoken to his local newspaper, the Richland Washington Villager, and was among the first witnesses to suggest extraterrestrial origins: "I believe it may be a visitor from another planet."Michael D. Hall & Wendy A. Connors, Alfred Loedding & the Great Saucer Wave of 1947, online, p. 27

About west-northwest of Richland in Yakima, Washington, a woman named Ethel Wheelhouse likewise reported sighting several flying discs moving at fantastic speeds at around the same time as Arnold's sighting.Hall & Connors, 27

When military intelligence began investigating Arnold's sighting in early July (see below), they found yet another witness from the area. A member of the Washington State forest service, who had been on fire watch at a tower in Diamond Gap, about south of Yakima, reported seeing "flashes" at 3:00 p.m. on the 24th over Mount Rainier (or exactly the same time as Arnold's sighting), that appeared to move in a straight line. Similarly, at 3:00 p.m. Sidney B. Gallagher in Washington state (exact position unspecified) reported seeing nine shiny discs flash by to the north.Hall & Connors, 27–28

Other Seattle area newspapers also reported other sightings of flashing, rapidly moving unknown objects on the same day, but not the same time, as Arnold's sighting. Most of these sightings were over Seattle or west of Seattle in the town of Bremerton, either that morning or at night.Seattle Daily Times, June 27, 1947, p. 1; Bremerton Sun, June 28, 1947, p. 1

The primary corroborative sighting, however, occurred ten days later (July 4) when a United Airlines crew over Idaho en route to Seattle also spotted five to nine disk-like objects that paced their plane for 10 to 15 minutes before suddenly disappearing.

Arnold talks of possible non-earthly origins On July 7, 1947, two stories came out where Arnold raised the topic of possible extraterrestrial origins, both as his opinion and those who had written to him. In an Associated Press story, Arnold said he had received quantities of fan mail eager to help solve the mystery, none of it calling him a "screwball". Many of the writers, like a doomsday preacher Arnold spoke of, placed a religious interpretation on his sighting. But others, he said, "suggested the discs were visitations from another planet." Arnold added he had purchased a movie camera, which he would now take with him on every flight, hoping to obtain photographic proof of what he had seen.Associated Press story, July 7, 1947, e.g., Salt Lake City Deseret News, p. 3, "Author of 'Discs' Story To Seek Proof"

In the other story, Arnold was interviewed by the Chicago Times:

In an Associated Press story from July 19, Arnold reiterated his belief that if they weren't Army, then they were extraterrestrial:Walla Walla (Wash) Union-Bulletin, July 20, 1947, "Man Who Reported 'Flying Saucers' Feels That He Has Been Vindicated"

In April 1949, in a skeptical article in the Saturday Evening Post titled "What You Can Believe About Flying Saucers", Arnold was likewise quoted:

In 1950, broadcaster Edward R. Murrow interviewed Arnold, who stated that since June 1947 he had had three additional sightings of nine spacecraft.

Publicity and origins of term "flying saucer"