Question: Raymond Palmer co-wrote The Coming of the Saucers with an American aviator and businessman who made what is considered the first widely reported unidentified flying object sighting when?

full_context: Document 1: Steve Fossett: James Stephen "Steve" Fossett (April 22, 1944 – c. September 3, 2007) was an American businessman and a record-setting aviator, sailor, and adventurer. He was the first person to fly solo nonstop around the world in a balloon. He made his fortune in the financial services industry and was best known for many world records, including five nonstop circumnavigations of the Earth: as a long-distance solo balloonist, as a sailor, and as a solo flight fixed-wing aircraft pilot.
Document 2: Kaikoura lights: The Kaikoura lights is a name given by the New Zealand media to a series of UFO sightings that occurred in December 1978, over the skies above the Kaikoura mountain ranges in the northeast of New Zealand's South Island. The first sightings were made on 21 December when the crew of a Safe Air Ltd cargo aircraft began observing a series of strange lights around their Armstrong Whitworth AW.660 Argosy aircraft, which tracked along with their aircraft for several minutes before disappearing and then reappearing elsewhere, the UFO was very large and had five white flashing lights that were visible on the craft. Some people say that they could see some little disks drop from the UFO and then disappear (they were never found). The pilots described some of the lights to be the size of a house and others small but flashing brilliantly. These objects appeared on the air traffic controller radar in Wellington and also on the aircraft's on-board radar.
Document 3: Kenneth Arnold UFO sighting: The Kenneth Arnold UFO sighting occurred on June 24, 1947, when private pilot Kenneth Arnold claimed that he saw a string of nine, shiny unidentified flying objects flying past Mount Rainier at speeds that Arnold estimated at a minimum of 1,200 miles an hour (1,932 km/hr). This was the first post-War 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.
Document 4: Kenneth O. Chilstrom: Kenneth O. "K.O." Chilstrom (born April 20, 1921) is a retired United States Air Force officer, combat veteran, test pilot, and author. He was the first USAF pilot to fly the XP-86 Sabre, chief of fighter test at Wright Field, commandant of the U.S. Air Force Test Pilot School, and program manager for the XF-108 Rapier. Chilstrom was a pilot in the first jet air race and delivered the first air mail by jet. He flew over eighty combat missions in the Italian Campaign of World War II and tested over twenty foreign models of German and Japanese fighters and bombers to evaluate their strengths and weaknesses.
Document 5: Raymond A. Palmer: Raymond Arthur Palmer (August 1, 1910 – August 15, 1977) was an American editor of "Amazing Stories" from 1938 through 1949, when he left publisher Ziff-Davis to publish and edit "Fate Magazine", and eventually many other magazines and books through his own publishing houses, including Amherst Press and Palmer Publications. In addition to magazines such as "Mystic," "Search," and 'Flying Saucers," he published numerous spirtualist books, including "", as well as several books related to flying saucers, including "The Coming of the Saucers," co-written by Palmer with Kenneth Arnold. Palmer was also a prolific author of science fiction and fantasy stories, many of which were published under pseudonyms.
Document 6: Imagination (magazine): Imagination was an American fantasy and science fiction magazine first published in October 1950 by Raymond Palmer's Clark Publishing Company. The magazine was sold almost immediately to Greenleaf Publishing Company, owned by William Hamling, who published and edited it from the third issue, February 1951, for the rest of the magazine's life. Hamling launched a sister magazine, Imaginative Tales, in 1954; both ceased publication at the end of 1958 in the aftermath of major changes in US magazine distribution due to the liquidation of American News Company.
Document 7: Vargo Statten Science Fiction Magazine: Vargo Statten Science Fiction Magazine (later Vargo Statten British Science Fiction Magazine, The British Science Fiction Magazine and The British Space Fiction Magazine) was a British science fiction magazine which published nineteen issues between 1954 and 1956. It was initially published by Scion Press, with control passing to a successor company, Scion Distributors, after Scion went bankrupt in early 1954. At the end of 1954, as part payment for a debt, Scion Distributors handed control of the magazine to Dragon Press, who continued it for another twelve issues. E.C. Tubb and John Russell Fearn were regular contributors, and Kenneth Bulmer also published several stories in the magazine. Barrington Bayley's first published story, "Combat's End", appeared in May 1954. The editor was initially Alistair Paterson, but after seven issues Fearn took the helm: "Vargo Statten" was one of Fearn's aliases, and the magazine's title had been chosen because of his popularity. Neither Paterson nor Fearn had enough of a budget to attract good quality submissions, and a printing strike in 1956 brought an end to the magazine's life.
Document 8: Science-Fiction Plus: Science-Fiction Plus was a U.S. science fiction magazine published by Hugo Gernsback for seven issues in 1953. In 1926 Gernsback had launched "Amazing Stories," the first science fiction magazine, but he had not been involved in the genre since 1936, when he sold "Wonder Stories". "Science-Fiction Plus" was initially in slick format, meaning that it was large-size and printed on glossy paper. Gernsback had always believed in the educational power of science fiction, and he continued to advocate his views in the new magazine's editorials. The managing editor, Sam Moskowitz, had been a reader of the early pulp magazines, and published many writers who had been popular before World War II, such as Raymond Gallun, Eando Binder, and Harry Bates. Combined with Gernsback's earnest editorials, the use of these early writers gave the magazine an anachronistic feel. Sales were initially good, but soon fell. For the last two issues Gernsback switched the magazine to cheaper pulp paper, but the magazine remained unprofitable. The final issue was dated December 1953.
Document 9: Sperry UFO case: The Sperry UFO case was a sighting of an Unidentified Flying Object by the captain, Willis Sperry, and other crew of an American Airlines DC-6 airborne near Mount Vernon, Maryland on 29 May 1950.
Document 10: Analog Science Fiction and Fact: Analog Science Fiction and Fact is an American science-fiction magazine published under various titles since 1930. Originally titled Astounding "Stories of Super-Science", the first issue was dated January 1930, published by William Clayton, and edited by Harry Bates. Clayton went bankrupt in 1933 and the magazine was sold to Street & Smith. The new editor was F. Orlin Tremaine, who soon made "Astounding" the leading magazine in the nascent pulp science fiction field, publishing well-regarded stories such as Jack Williamson's "Legion of Space" and John W. Campbell's "Twilight". At the end of 1937, Campbell took over editorial duties under Tremaine's supervision, and the following year Tremaine was let go, giving Campbell more independence. Over the next few years Campbell published many stories that became classics in the field, including Isaac Asimov's "Foundation" series, A.E. van Vogt's "Slan", and several novels and stories by Robert A. Heinlein. The period beginning with Campbell's editorship is often referred to as the Golden Age of Science Fiction.
Document 11: Cosmic Stories and Stirring Science Stories: Cosmic Stories (also known as Cosmic Science-Fiction) and Stirring Science Stories were two American pulp science fiction magazines that published a total of seven issues in 1941 and 1942. Both "Cosmic" and "Stirring" were edited by Donald A. Wollheim and launched by the same publisher, appearing in alternate months. Wollheim had no budget at all for fiction, so he solicited stories from his friends among the Futurians, a group of young science fiction fans including James Blish and C. M. Kornbluth. Isaac Asimov contributed a story, but later insisted on payment after hearing that F. Orlin Tremaine, the editor of the competing science fiction magazine "Comet", was irate at the idea of a magazine that might "siphon readership from magazines that paid", and thought that authors who contributed should be blacklisted. Kornbluth was the most prolific contributor, under several pseudonyms; one of his stories, "Thirteen O'Clock", published under the pseudonym "Cecil Corwin", was very successful, and helped to make his reputation in the field. The magazines ceased publication in late 1941, but Wollheim was able to find a publisher for one further issue of "Stirring Science Stories" in March 1942 before war restrictions forced it to close again.
Document 12: Kenneth Arnold: Kenneth A. Arnold (March 29, 1915 – January 16, 1984) was an American aviator and businessman. He is best known for making what is generally considered the first widely reported unidentified flying object sighting in the United States, after claiming to have seen nine unusual objects flying in tandem near Mount Rainier, Washington on June 24, 1947.
Document 13: World UFO Day: World UFO Day is an awareness day for people to gather together and watch the skies for unidentified flying objects. The day is celebrated by some on June 24, and others on July 2. June 24 is the date that aviator Kenneth Arnold reported what is generally considered to be the first widely reported unidentified flying object sighting in the United States, while July 2 commemorates the supposed UFO crash in the 1947 Roswell UFO Incident.
Document 14: Nash-Fortenberry UFO sighting: The Nash-Fortenberry UFO sighting was an unidentified flying object sighting that occurred on July 14, 1952, when two commercial pilots (William B. Nash and William H. Fortenberry) claimed to have seen eight UFOs flying in a tight echelon formation over Chesapeake Bay in the state of Virginia.
Document 15: Unknown (magazine): Unknown (also known as Unknown Worlds) was an American pulp fantasy fiction magazine, published from 1939 to 1943 by Street & Smith, and edited by John W. Campbell. "Unknown" was a companion to Street & Smith's science fiction pulp, "Astounding Science Fiction", which was also edited by Campbell at the time; many authors and illustrators contributed to both magazines. The leading fantasy magazine in the 1930s was "Weird Tales", which focused on shock and horror. Campbell wanted to publish a fantasy magazine with more finesse and humor than "Weird Tales", and put his plans into action when Eric Frank Russell sent him the manuscript of his novel "Sinister Barrier", about aliens who own the human race. "Unknown"' s first issue appeared in March 1939; in addition to "Sinister Barrier", it included H. L. Gold's "Trouble With Water", a humorous fantasy about a New Yorker who meets a water gnome. Gold's story was the first of many in "Unknown" to combine commonplace reality with the fantastic.
ground_truth: June 24, 1947