Aviation accident analysis is performed to determine the cause of errors once an accident has happened. In the modern aviation industry, it is also used to analyze a database of past accidents in order to prevent an accident from happening. Many models have been used not only for the accident investigation but also for educational purpose. ICAO Annex 13—Aircraft Accident and Incident Investigation—defines which States may participate in an investigation, for example: the States of Occurrence, Registry, Operator, Design and Manufacture.