An error that does not cause an accident but still causes a problem is known as an incident. Some incidents are more high profile than others, such as errors causing significant in-flight events that, fortuitously, or because of the skills of the pilot, did not become accidents. Other incidents are more mundane and do not become serious because of defenses built into the maintenance system. However, all incidents are significant to the aircraft maintenance industry, as they may warn of a potential future accident should the error occur in different circumstances. It is likely that most errors made by aircraft maintenance engineers are spotted almost immediately and corrected. The engineer may detect his own error, or it may be noticed by colleagues, supervisors or quality control. In these cases, the engineer involved should learn from his error and therefore be less likely to make the same error again.