With any complex dynamic system where man plays an important role of supervision and control, the use of a working tool for training raises a problem of safety and efficiency for the users of the system concerned. The development of sophisticated simulators has solved this problem in the field of air traffic control. The description shows that these simulators use the same technologies as those used in operational centres: very high-definition display system with stroke or TV scan, advanced programming language ADA, etc. Finally, a few research subjects such as speech recognition and artificial intelligence are presented to illustrate possible evolutions of these training systems.