The rate of error in the performance of any task increases rapidly after a certain degree of complexity or rate of operation is exceeded. As aircraft speeds increase, therefore, the safety and efficiency of the operation will depend largely on the extent to which the job of the crew can be simplified and on the work-load being kept within tolerable limits. In recent years the problem has been tackled by the addition of specialist crew members and by the use of automatic and semi-automatic equipment. Distribution of the total load over an increased number of people is no longer a satisfactory solution, however, since it imposes an additional burden on the Captain in his capacity as overall monitor and the time available for this vital task is all too little. While the pilot by tradition tends to reserve judgment on automatic devices generally, where a high standard of reliability is proved the system will receive acceptance in due course and there is little doubt that it is in this field where the greatest contribution to operating efficiency will be found.