In aviation, the sterile flight deck rule or sterile cockpit rule is a procedural requirement that during critical phases of flight (normally below 10,000 feet (3,050 m)), only activities required for the safe operation of the aircraft may be carried out by the flight crew, and all non-essential activities in the cockpit are forbidden. In the United States, the Federal Aviation Administration (FAA) imposed the rule in 1981, after reviewing a series of accidents that were caused by flight crews who were distracted from their flying duties by engaging in non-essential conversations and activities during critical parts of the flight.