To prevent errors from occurring, it is necessary to predict where they are most likely to occur and then to implement preventative measures. It is very difficult to list all means by which errors might be prevented or minimized in aircraft maintenance. In fact, this document discusses error prevention mechanisms, from ensuring that individuals are fit and alert, to making sure that the hangar lighting is adequate. The most effective means of preventing error is to ensure that engineers follow procedures by maintaining correct and usable procedures, presenting user friendly information appropriate to the task and context and encouraging engineers to follow procedures, rather than cutting corners.