Flight simulators for pilot training are constantly evolving, and their role in the training process is becoming increasingly important. The synthetic environment is used during the initial phases of training, in familiarisation with the aircraft, and then maintains its importance in the subsequent phases, culminating in training for mission-critical and safety-critical procedures. The simulation devices, although having different levels of complexity, realism and fidelity compared to the real aircraft, are linked by a common set of standards and requirements, coming from the designated National and Supranational Authorities, which must be met to allow the certification of simulators. This suitability is also demonstrated through objective tests that link the behaviour of the simulated aircraft within the synthetic environment with the real aircraft performances, by comparing flight manoeuvres accomplished in the simulator with the same manoeuvres recorded in flight.