When, last year, you elected me to be your President, you placed upon me the duty of delivering before the Institute the tenth Presidential Address. My predecessors in this office have been men of considerable scientific and administrative distinction, able to talk with authority in their respective fields of learning. I, however, come before you mainly as a practitioner of air navigation, the first such to be your President, concerned with the practical business of ‘how to get there’ in an imperfect, and only partly understood, world, rather than with the elegant demonstrations of a theoretical technology. The duty of preparing a Presidential Address, though onerous, has its compensations. It is the one occasion in the Institute's year when a speaker has the right to stand up before you, and to muse and speculate on controversial matters, rather than to present an account of completed work. A recent writer speculating on the future growth of air transport took as his motto: ‘Behold the turtle—she advances only by sticking her neck out’. This is true not only of turtles, but exemplifies the spirit which is needed to meet the challenge of the future: it is in such a spirit that I offer this Address.