 In 1998, the FAA published Order 8040.4, establishing risk management policy including hazard analysis in a range of critical activities beyond aircraft certification, including air traffic control and modernization of the U.S. National Airspace System.This led to the publication of the FAA System Safety Handbook, which describes the use of FTA in various types of formal hazard analysis.Early in the Apollo program the question was asked about the probability of successfully sending astronauts to the moon and returning them safely to Earth.