I am deeply conscious of the privilege of giving this First Joint Lecture of the Royal Aeronautical Society and the Society of Licensed Aircraft Engineers and Technologists. I am delighted this has been initiated by our two bodies. Our close working together can only be to the benefit of aviation as a whole in this country. It is also another step in bringing closer together those concerned with research, development, and design with those of us concerned with maintenance. In these days of high costs of equipment and of labour, I am glad to say that maintenance is at last being recognised as requiring a much larger degree of attention at the initiation of projects than has been the case in the past. Moreover, it gives me particular pleasure that a Royal Air Force lecturer should be invited on this occasion because of the very close affiliation of the work of engineers in the Royal Air Force with that of the members of SLAET.