Kenneth Arnold, June 24, 1947: the sighting that invented "flying saucers"

At a glance

• When: Tuesday, June 24, 1947, around 3 p.m. local time².
• Where: over the Cascades, between Mount Rainier and Mount Adams, Washington State².
• Who: Kenneth Arnold, 32, a businessman from Boise, Idaho, and private pilot, flying his single-engine CallAir^2,3.
• What: nine very bright, flat objects flying in a chain from north to south, at an estimated speed of 1,200 to 1,700 mph^2,8.
• US Air Force conclusion: "mirage"⁸. It is not the only official conclusion the case received.

The flight of June 24, 1947

At around 2 p.m., Kenneth Arnold took off from Chehalis, Washington, for Yakima². He allowed himself an hour's detour to search the southwest slope of Mount Rainier for a large Marine Corps transport plane lost in the mountains². Edward Ruppelt, later head of Project Blue Book, would specify that it was a C-46¹⁷.

He climbed to about 9,500 feet, the elevation of the plateau from which Rainier rises, swept the area, made a full turn over the small town of Mineral, then resumed his course east at about 9,200 feet². The air was so smooth that he let go of the controls, and, he wrote, "the sky and air was as clear as crystal"². Far off to his left and behind, a four-engine DC-4 was flying at 14,000 feet, about fifteen miles away².

Nine objects between Rainier and Adams

Two or three minutes later, a flash reflected on his plane. Looking for its source, Arnold saw to the left and north of Rainier "a chain of nine peculiar looking aircraft" flying from north to south at about 9,500 feet, on a heading of about 170 degrees². Every few seconds, two or three of them would dip or bank slightly, just enough for the sun to strike them².

He compared them to geese: they flew "in a rather diagonal chain-like line as if they were linked together", weaving between the peaks². What puzzled him was that he could not make out any tail on them². He put their distance at 20 to 25 miles, seen almost at a right angle². To judge their size he compared them with the DC-4: smaller, but with a span comparable to the distance between the airliner's outer engines².

To rule out a reflection, he said he watched through the windshield, then turned the plane so he could open his window, without sunglasses². Edge-on, the objects were "just a black thin line"; when the sun reflected off them, they looked "completely round"². In the sketch attached to his report they are rounded at the front, cut off at the back and very thin, with the caption "They seemed longer than wide, their thickness was about 1/20th of their width", and "Mirror Bright"².

The whole sighting lasted "around two and one-half or three minutes"². Arnold kept searching for another quarter of an hour, then headed for Yakima².

An impossible speed for 1947

Arnold reacted like a pilot: he timed them. His dashboard clock read one minute to 3 p.m. as the first object passed the southern edge of Rainier. When the last one cleared the southern crest of Mount Adams, the second hand had covered one minute and forty-two seconds². He also put the length of the chain at five miles at least, comparing it with a snow-covered ridge between the two peaks².

He only measured the distance between the two mountains once he reached Pendleton². The arithmetic is simple and dizzying. The Air Force summary used 47 miles in 102 seconds, or 1,656 mph⁸. The astronomer J. Allen Hynek, consulting for the military, rounded it to 1,700 mph⁶. Arnold himself gave the press a more cautious figure of "around 1,200 miles an hour"^12,13. On the radio he added that even "giving" them three or four minutes, the speed would still exceed 800 mph¹². For comparison, the speed record at the time, held by a P-80 jet fighter, was 647 mph¹⁰.

From Pendleton to the whole world: the birth of "flying saucers"

On the morning of June 25, Arnold walked into the East Oregonian, the daily paper in Pendleton, Oregon. Bill Bequette, then 28, described the scene in 1998: Nolan Skiff jotted down a few notes and wrote a short story, which Bequette squeezed into the bottom of the front page before punching an even shorter version into the Associated Press wire¹⁵. The article said Arnold had seen "nine saucer-like aircraft", "extremely bright, as if they were nickel plated"¹³. Arnold was quoted: "It seemed impossible… but there it is – I must believe my eyes"¹³.

That afternoon Bequette spent two hours with Arnold at his hotel and phoned a long piece to the AP office in Portland. "Next morning almost every newspaper in the country published the story on page one," he recalled¹⁵. On June 26 the Chicago Sun ran on page 2: "Supersonic Flying Saucers Sighted by Idaho Pilot"¹⁴.

The same day, the AP carried official scepticism. An Army spokesman in Washington said that as far as he knew, "nothing flies that fast except a V-2 rocket"¹⁰. Arnold, besieged by calls, told United Press he had not "had a moment of peace" since telling his story¹⁰. On June 30 the AP wrote that Westerners were seeing "flying saucers" "almost everywhere today from Canada to Texas"¹⁰. On July 8 a headline summed up the fever: "Who Has the Saucer? 40 States Join Game"¹⁰. That same day, the FBI office in Dallas reported that a "flying disc" had been recovered near Roswell, New Mexico²⁴.

"Flying saucer": who actually said it?

The most widespread version holds that Arnold described the objects' motion, like a saucer skipping across water, and that a reporter turned the comparison into a shape. Arnold said so himself on CBS radio in 1950: "They said that I said that they were saucer-like; I said that they flew in a saucer-like fashion"¹⁶. The Air Force summary repeats this: the description was "shortened to flying saucers by some of the newspaper men"⁸. The sceptic Martin Kottmeyer turned it into a thesis, "The Saucer Error": the saucer image was born of a misunderstanding and then shaped the sightings that followed²⁰.

The 1947 documents complicate this story. In his own written report to the military in July 1947, Arnold himself wrote of "saucer like objects" and "saucer-like disks"². On the radio on June 26, he described their shape as "something like a pie plate that was cut in half, with a sort of a convex triangle in the rear"¹². As for Bill Bequette, he always denied coining the phrase: "I'm sure I didn't coin 'flying saucers'"¹⁵. The analyst Martin Shough, who reconstructed the chronology of Arnold's statements, concludes that the pure newspaper-misunderstanding thesis is partly a later reconstruction¹⁹.

The military investigates

In early July, Arnold sent the Commanding General at Wright Field, Ohio, a seven-page typed report with his sketch². It opens: "The following story of what I observed over the Cascade mountains, as impossible as it may seem, is positively true"². On July 12 he sent a telegram authorising the military to quote, give out or reprint the report. He regretted that no one had given him an explanation, as he "felt certain they belonged to our government"⁴.

That same July 12 he was interviewed in Boise by Frank M. Brown, a special agent of the Counter Intelligence Corps, 4th Air Force³. Brown's memo, dated July 16, is unambiguous: "It is the personal opinion of the interviewer that Mr. Arnold actually saw what he stated that he saw"³. Checked against an aeronautical chart, his statements on distance, speed, heading and size "could very possibly be facts"³. Brown also noted that Arnold was "very outspoken and somewhat bitter" towards the Army Air Forces and the FBI for not investigating sooner. Arnold said that in future, "if I saw a ten story building flying through the air I would never say a word about it"³.

Brown and his colleague, Captain William L. Davidson, died a few weeks later. On August 1, 1947, their plane crashed at Kelso, Washington, on the way back from an investigation in Tacoma, the so-called Maury Island affair, in which Arnold had become involved¹¹. Edward Ruppelt later called it a hoax: "the first, possibly the second-best, and the dirtiest hoax in the UFO history"¹⁷.

Four official conclusions for one case

The Air Force file contains several successive evaluations, and they do not agree.

Who	When	Conclusion
Frank M. Brown, Counter Intelligence Corps	July 16, 1947	Arnold saw what he describes; his figures are plausible3
J. Allen Hynek, astronomer, Project Sign	1948–1949	No astronomical explanation; the objects were probably closer and slower, possibly known aircraft6
Air Materiel Command, Project Grudge	1949	The report "cannot bear even superficial examination" and must be disregarded7
Final Project Blue Book record	form edition of 1963	"Other (MIRAGE)"8

Hynek's reasoning rests on visual acuity. At 25 miles, for Arnold to make out the objects' thickness, they would have had to be at least 100 feet thick and 2,000 feet long. And if they were only 45 to 50 feet, he could not have seen them at all. "If Arnold actually saw the objects, and if his estimate of distance is correct, that of size cannot be, and vice versa"⁶. Assuming a size of 400 feet at most, Hynek brought the objects to six miles and about 400 mph, a subsonic speed consistent with "some sort of known aircraft"⁶. Yet he also wrote that there "appears to be no astronomical explanation for this classic incident, which is the prototype of many of the later flying saucer stories", and placed the case in the category "non-astronomical, with no explanation evident"⁶.

The Air Materiel Command was harsher: the report is "replete with inconsistencies", and the observer "has profited from this story by selling it to Fate magazine". It added that the report and its publicity were "largely responsible" for the reports that followed⁷.

The final Project Blue Book record concludes "mirage". The argument: the "smooth" and "crystal clear" air Arnold described suggests very stable conditions, favourable to temperature inversions that bend light⁸. The same record gives the course as "West", whereas Arnold always described a north-to-south flight^8,2. And Edward Ruppelt, who ran Blue Book, wrote in 1956 that the case sat in the files as just another "unknown"¹⁷.

The explanations put forward since

Hypothesis	Put forward by	The problem
Jet aircraft closer than estimated	Hynek (1948–1949)6	No pilot ever came forward; Arnold could make out the DC-4's engines at about 15 miles, which Hynek's acuity criterion would rule out18; Shough considers the criterion misapplied19
Mirage	US Air Force, Project Blue Book8	A mirage explains neither the rapid sideways motion nor the passage in front of the ridges18
Mountain wave clouds	Donald Menzel and Lyle Boyd (1963)9	Such clouds stay almost stationary21
Snow blown off the peaks	Donald Menzel (1953)	Ruppelt reports the reply of a pilot who knew the area: impossible in June17
Fragmenting meteors	Keay Davidson (1997), relayed by Philip Klass22	A meteor does not go out and light up again, nor fly level for two minutes18
Birds (swans or geese; pelicans)	Martin Kottmeyer (1997)21; James Easton, cited by other authors25	Arnold himself compared them to geese, but the altitude and distance require assuming a large estimation error21
Secret US aircraft	Arnold himself in July 19472,4	The military denied it, publicly and in its exchanges with the FBI18

Bruce Maccabee, a physicist who favours an unexplained phenomenon, considers that no credible mundane explanation has been offered¹⁸. Martin Shough concludes after a meticulous analysis that there is "no internal reason to question Arnold's timing report", which says nothing about what the objects were¹⁹.

Where the accounts disagree

Point	According to the sources
Take-off time	"about two o'clock" (report); "about 2:15" (radio, June 26)2,12
Objects' heading	170° (report); 160° (radio); "West" on the Blue Book record, contrary to all of Arnold's statements2,12,8
Timing landmarks	Rainier and Adams (report); "Mt. Saint Helens and Mt. Adams" (radio)2,12
Distance	20 to 25 miles (report); 25 to 30 miles (AP, June 26); 6 miles at most according to Hynek2,10,6
Size	smaller than the DC-4 (report); "as big as a DC-4" (AP); "45 to 50 ft" in an anonymous summary in the file, a figure that is not Arnold's2,10,5,19
Speed	1,200 mph (Arnold); 1,656 mph (US Air Force); 1,700 (Hynek); "approx 150 MPH" on a checklist, an obvious error12,8,6,5
Shape	round in the sun, a thin line edge-on, cut off at the back (report); "a pie plate that was cut in half" (radio); later, one crescent-shaped object2,12,19
Date	Brown's memo places the sighting on "July 25th" instead of June 243

The legacy

Kenneth Arnold's objects looked nothing like the round, domed saucers that took over popular imagination. Yet his sighting gave the phenomenon its name and opened the great wave of summer 1947. The military itself judged in 1949 that his account and its publicity were "largely responsible" for the reports that followed⁷. In his report Arnold said he was "convinced in my own mind that they were some type of airplane"². He died in 1984, aged 68²³.

The complete 61-page US Air Force file is freely available at the US National Archives¹. The main documents are reproduced below.