A Beech Bonanza, N 3794N, crashed at night approximately 5 miles northwest of the Mason City Municipal Airport, Mason City, Iowa, at approximately 01:00, February 3, 1959. The pilot and three passengers were killed and the aircraft was demolished.The aircraft was observed to take off toward the south in a normal manner, turn and climb to an estimated altitude of 800ft, and then head in a northwesterly direction. When approximately 5 miles had been traversed, the tail light of the aircraft was seen to descend gradually until it disappeared from sight. Follow this, many unsuccessful attempts were made to contact the aircraft by radio. The wreckage was found in a field later that morning.This accident, like so many before it, was caused by the pilot’s decision to undertake a flight in which the likelihood of encountering instrument conditions existed, in the mistaken belief that he could cope with en route instrument weather conditions, without having the necessary familiarization with the instruments in the aircraft and without being properly certificated to fly solely by instrument. 5.What caused the accident?