A general review of the state-of-the-art in relation to stability augmentation in aircraft design, with an attempt to produce a co-ordinated view on the philosophy of its application, is something that I have long felt I should like to see done—but not by myself. My initial reaction on being asked to present such a paper was that this would better come from those concerned with the development of auto-control systems, but on second thoughts, there appeared to be some merit in considering the situation from the point of view of one concerned with the more basic aspects of aircraft handling and operation, putting the emphasis, therefore, on what is required or desirable in these respects, rather than on how it might be achieved. This, then, is my first aim; to consider various possible areas of application of stability augmentation, and advanced control techniques, to aircraft design; my survey will not attempt to be comprehensive but rather, selectively illustrative; it will, however, extend out beyond the confines of pure aircraft design, to externally guided aircraft flight, and in particular automatic landing.