A high reliability organization (HRO) is an organization that has succeeded in avoiding catastrophes in an environment where normal accidents can be expected due to risk factors and complexity. Important case studies in HRO research include both studies of disasters (e.g., Three Mile Island nuclear incident, the Challenger explosion and Columbia explosion, the Bhopal chemical leak, the Tenerife air crash, the Mann Gulch forest fire, the Black Hawk friendly fire incident in Iraq) and HROs like the air traffic control system, naval aircraft carriers, and nuclear power operations.