Reliability and safety criteria have, in one form or another, made a significant contribution to engineering design since the earliest times. They gained added significance in Victorian times as the scale of civil and mechanical engineering projects increased. Codes of practice came into use, based both on practical experience and theoretical knowledge. Redundancy and diversity, though not given those names, were introduced as a means of achieving improved reliability and safety. Reliability and safety technology in the modern sense only developed, however, when predictive techniques, based on statistical information, were introduced. This technology has now taken its place in a wide range of engineering activities and is adopting an increasingly international role. It makes use of numerical reliability and safety goals and pays attention to problems associated with human reliability and ergonomics. This paper reviews the particularly important contribution made by civil aviation to the development of present day reliability and safety technology.