A recently completed preliminary long-term study of air traffic control systems in Europe1 suggests that traffic density is likely at least to double before the end of the century. The study also concludes that, apart from the problem of airport capacity, which was not considered, the existing ATC systems in Europe will not be able to cope with such an increase in traffic. There is therefore a need to consider methods of increasing the capacity of the European ATC system or providing a new system and, in view of the time required to effect significant changes to such systems, the task is becoming urgent.

Assumingthere is to be no deterioration insafety, theprime requirements for any proposed changes are economy and flexibility. Apart from its obvious intrinsic value, economy is necessary because there is an increasing trend towards recovering the total cost of ATC from the user. Higher charges are therefore likely to stultify the growth in air transport and an underlying assumption is that this would be undesirable. Flexibility is required because traffic forecasts so far into the future are likely to be in error and the system design must allow for this because there is likely to be some economic penalty if the forecast proves to be either too high or too low.