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?
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.
i don't know