The CAB released a final report on the accident on January 10, 1960. The investigators concluded that the crew had been preoccupied with aspects of the flight and had neglected to monitor essential flight instruments during the descent, leading to a premature descent below landing minimums. Contributing to the accident were factors including the crew's limited experience with the aircraft type, a faulty approach technique in which the autopilot was used to or almost to the surface, an erroneous setting of the pilot's altimeter, marginal weather in the approach area, possible misinterpretation of the altimeter and the rate of descent indicators on the aircraft, and the crew's sensory illusion with respect to height and altitude resulting from a lack of visual references. The board was critical of the airline's lack of adequate simulator training on the aircraft before placing it into passenger service, and made recommendations to the FAA that all large turbine-engine aircraft used in air transportation be equipped with a flight data recorder. Over 90 percent of the primary structural components of the aircraft and most of the system's components were recovered by investigators. They found that at the moment of impact, the flaps were approximately in the approach position, the landing gear was extended, and propeller blade angles were relatively uniform and consistent with the power readings obtained from the recovered aircraft instruments and consistent with the testimony of the crew regarding the power being used during the approach. Neither of the two vertical speed indicator mechanisms were recovered. Both altimeters were recovered, but since the diaphragms of both had been overstressed due to submersion, it was impossible to establish the calibration or accuracy of either altimeter before the crash. Investigators obtained all of the maintenance records including pilot complaints of all operators, civil and military, of the type of altimeter used in the flight. None of the reported incidents involved more than one of the altimeters installed at a time, and after reviewing the possibility of a simultaneous failure of both altimeters, the CAB concluded that it would involve such an extreme mathematical improbability that it chose to reject that theory as well as reject portions of the testimony of the surviving crew members. It also concluded that after consideration of all possible scenarios, that a failure of just one of the altimeters was also unlikely to have occurred. Based upon eyewitness testimony and analysis of