Over the better developed land areas of the world, where radio and communication facilities enable aircraft positions to be known on the ground, the system of Airways flying has been introduced. In areas of high traffic density it is of the greatest value, as it allows the traffic control authorities to separate aircraft at moderate to close intervals. The system requires good and continuous radio track guidance and a regular reporting procedure at specific radio fixes. (Airways are normally looked upon as fully controlled areas and until some more reliable long-range aid which can present continuous fixing is developed, Oceanic Airways would be more properly referred to as Oceanic ADR's.)