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?
Raymond A. Palmer:  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. Kenneth Arnold: Kenneth A. Arnold (March 29, 1915 – January 16, 1984) was an American aviator and businessman. Kenneth Arnold:  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.
June 24, 1947