The subject of air navigation has been chosen because with the ending- of the Wiar this becomes the most important of the unsohed problems relating to aviation. It is unsolved mainly, I think, because the actual operations of the war, apart from certain individual efforts of great merit, did not reach the point at which really long flights were made. Had the activity of the Wiar continued there is little doubt that long distance air navigation would have been impelled to as high a degree of actual achievement as was attained by other branches of the new science of aeronautics.