The safety of civil aviation is the major objective of the International Civil Aviation Organization ICAO. It has long been known that the majority of aviation accidents and incidents result from less than optimum human performance, indicating that any advance in this field can be expected to have a significant impact on the improvement of aviation safety. Considerable progress has been made in increasing safety during years, but additional improvements are needed and can be achieved. One of the factors most responsible for the decline of human performance over time is fatigue, a common enemy for all shift workers. Human beings inevitably get fatigued, and when this happens attention drops and the probability of making a mistake increases; especially in the aviation field a single, trivial error can have a very high cost in term of human lives.