Human error has played an important role in accident causation. The problem of human error in aviation has turned out to be a difficult one both to understand and to solve. However, significant progress has been made over the past few years to achieve the understanding the nature and root causes of human error. Our hope is to develop solutions (better equipment, better selection tools for flight crews, better training etc.) through this understanding to the problem of human error, and hereby enhance flight safety. Furthermore, we must be able to predict with some certainty what conditions in flight are the most likely to cause the types of errors in order to have control over these errors. Since human behavior is complex, an adequate model for linking components of pilots, machinery, and the other human actors should tie back into the rich experimental and theoretical literature on human behavior.