United States.Kenneth Arnold · nine bright objects near Mount Rainier

On June 24, 1947, in the early afternoon, Kenneth Arnold (a fire-suppression-products businessman and experienced private pilot from Boise, Idaho) took off from Chehalis, in southwestern Washington state, heading east to Yakima in his two-seat CallAir A-2. He made a detour over the Cascade Range to search for a downed military transport (a Marine Corps C-46 lost near Mount Rainier) for which a $5,000 reward was offered. Around 3:00 p.m., a flash made him look north: he said he saw nine bright, flat objects flying in a staggered formation between Mount Rainier and Mount Adams.

His account, picked up on June 25 and carried by the national press, triggered the wave of sightings in the summer of 1947 (the Roswell announcement came two weeks later).

In the written report he gave Army Air Forces intelligence on July 12, Arnold said he was flying at about 9,200 feet, with a DC-4 to his left and rear, and saw to his left, north of Rainier, a chain of nine objects flying north to south at roughly his own altitude on a heading of about 170 degrees. At first he took them for jets, but could find no tails; every few seconds two or three of them would dip or change course slightly and the sun struck flashes from them. He put them at 20 to 25 miles away, gave them a span similar to a DC-4 (about 45 to 50 feet) and a chain about five miles long.

To estimate their speed, he timed them with his panel clock at 1 minute 42 seconds between Rainier and Adams, 47 miles by his reckoning (about 76 km), which the file itself turns into 1,656.71 miles per hour; to the press he had first given 1,200.

In 1947 he described them as flat, "like a pie pan," so shiny they reflected the sun like a mirror, and the official form records an "approximately circular" shape; the crescent profile with a point reproduced today took hold in later versions, as Donald Menzel noted. The skipping-saucer phrase described the motion, not the shape, and from that misunderstanding the term "flying saucer" was born.

The Air Force file holds three official readings that do not agree. The agent who interviewed him in Boise wrote that Arnold had seen the discs and that, if he could write such a report without having seen them, he belonged in the business of writing Buck Rogers fiction. J. Allen Hynek, in his evaluation of incident 17, calculated that to make out so much detail at 20 to 25 miles the objects would have had to be at least 100 feet thick and some 2,000 feet long; that if the estimated size was right they were about six miles away and would have covered only 11 miles in 102 seconds, about 400 miles per hour; and he concluded that it "appears probable" they were subsonic and "may, therefore have been some sort of known aircraft." The Air Materiel Command went further: the report "cannot bear even superficial examination" and must be disregarded.

The Blue Book record card, written later, closed it as "Other (mirage)" on the strength of the stable air Arnold himself described, and the file keeps the analysis Menzel took from meteorologist Richard Reed on moving lenticular clouds. Meteors, canopy reflections and birds were also suggested. Arnold rejected those readings and kept to his account until his death in 1984. No explanation was proven.

Arnold's account gave the modern phenomenon its name and opened the 1947 wave; the Air Materiel Command attributed much of the later reporting to the publicity of this report.

The case rests on a single primary witness, with no radar, photo or film. Its most striking figure, the speed, is not a recording but Arnold's own measurement with his panel clock, and it is only as good as the distance he estimated by eye. None of the conventional explanations in the file was proven.