Simulation training of air traffic controllers will undergo major changes in the next few years. Central to the selection of a new ATC simulation training system is the issue of fidelity, both physical and functional. On the one hand, a very high level of fidelity is required to conduct advanced training in simulation labs rather than in the operational environment. However, the cost, particularly in staff resources, of providing and maintaining this level of realism limits its application to earlier phases of training.This paper recommends that the future simulation training system provide levels of fidelity appropriate to the level of training to which it is applied. This could be accomplished by either segmenting the capability of the full training system or through the provision of additional PC-based systems.