To claim that communications have unified our world is by now to voice a truism. Within the span of a generation we have thrust headlong into an age of transition and readjustment, the definitive trend of which is towards a world-wide mobility of goods, ideas, and the citizens who produce them. The role of the air route in this process is no longer a matter of dispute, and it is clear that the time has come to consider certain technical questions which underlie any detailed scheme for a truly international network of airways.