In 1990, the Transport Ministers of the European Civil Aviation Conference (ECAC) States, covering then Western Europe but now also Central and Eastern Europe, responded by adopting an ATC strategy for the 1990s which would harmonise and progressively integrate the patchwork of different ATC systems in Europe at present. The overall objective of the strategy is to improve airspace and control capacity whilst maintaining safety (Marten 1993). Eurocontrol - the European Organisation for the safety of air navigation - was chosen to manage the implementation of the strategy. It established the European Air Traffic Control Harmonisation and Integration Programme (EATCHIP) to implement the strategy for the en-route environment, comprising of four overlaping phases, the last of which relies upon major technical innovations to provide an ATC system for Europe for the future (Majumdar 1994). In most Western European en-route airspace sectors currently, the limiting factor on capacity is the workload of air traffic controllers, ie. the nature, complexity and duration of their tasks. This likely to remain so in the short to medium term (the next 25 years). Therefore controller workload will remain the dominant factor in determining sector and system capacity, and any modification of the airspace structure (air routes re-organisation, re-sectorisation, etc.) which reduces controller workload should increase airspace capacity.