The Board in this proceeding, in accordance with the statuatory mandate, is reporting the probable , not certain, cause of the accident. Undoubtedly, the Board's statuatory duty was thus defined in the Act in recognition of the fact, well known to the Congress, that due to the meager and inconclusive character of the evidence available, the circumstances surrounding air accidents have at times been shrouded in obscurity.
Probability flows from evidence which inclines the mind to a conclusion but leaves room for doubt.
Most of the subsidiary findings which follow, therefore, and certainly the conclusion as to the probable cause of the accident represent what appears to the Board to be the maximum of probability with respect to the several matters to which they relate. In some instances the conclusions lie in a twilight zone in which it has been extremely difficult to distinguish between probability and possibility. A mechanical adjustment made immediately prior to departure, to correct lowered oil pressure on one engine, was without significance with respect to the accident. The flight was dispatched in accordance with normal procedure, and all information in possession of the Weather Bureau and the company meteorologists had been taken into account in connection with the dispatch. The weather forecast contained nothing which would normally have raised any question about the advisability of dispatching a regular airline operation.