This module covers the human side of the operations concerning aircraft maintenance. With the high reliability and redundancy of aircraft systems in modern aircraft, most incidents and accidents can be attributed to some type of human caused input. Most incidents and accidents do not occur because of a single human failure but rather a chain of events. When designing aircraft and systems, maintenance activities and other procedures relating to the safe and efficient operation of a flight, many behaviors and inevitables are taken into account such as performance and limitations, psychology, fitness and health of individuals, schedules, physical environments and hazards, communications, types of work and tasks and error management. This module is typically required as recurrent training at specified intervals by national aviation authorities.