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accident. The past record of safety of air transportation within the United States, extending to over 130,000,000 miles of transport flying without serious injury to any person in the 17-month period immediately preceding the present accident and to thirteen years of operation without fatal accident by Pennsylvania Central Airlines and its predecessors, is a sufficient evidence that only the highly exceptional or the hitherto unknown would produce so tragic an effect. Since we are here necessarily dealing with occurrences of extreme rarity and consequent unfamiliarity and in some instances are considering phenomena of nature wherein the knowledge of men still remains extremely limited, it is inevitable that much of what follows must appear highly speculative. However, the inherent difficulties presented by the limited evidence available in the present case must not deter us from a full exploration of every possibility and an attempt to reach a conclusion as to what probably occurred to produce the accident.
Dispatch of the Flight
No reason has been discovered for believing that Trip 19 should not have been dispatched on August 31, 1940. The airplane had received a "60-hour" inspection at Detroit the day before the flight and had received the required "turn-around" inspection in Washington just before taking off and nothing unusual had been reported as a result of either of these inspections. The pilots who had brought the airplane down from Detroit to Washington that morning had not reported anything unusual in its operation. It was adequately serviced with fuel and oil. The load on board at the time of take-off was 174 pounds below the approved gross weight for the airplane and, according to the record,
