Applied aerodynamics and flight mechanics represent one of the many fields in which Dr. Theodore von Karman has made major contributions. His work has been especially valuable because of his theoretical and applied research on problems useful to those concerned with the design of airplanes. Such work has dealt with skin friction at subsonic and supersonic speeds, transonic similarity, linear supersonic theory, hypersonics, superaerodynamics, and the cost of speed. His survey papers, covering various speed ranges on subjects now of prime importance and given prior to the time when applied design progressed to these speed regions, represent milestones of foresight and progress. His broad interest in flight mechanics and related problems of applied mechanics in other fields has given his work breadth of coverage in subject matter and applicability. A design aerodynamicist has to consider carefully many aspects of each problem in order to achieve a well-balanced design. At subsonic speeds, turbulent skin friction comprises about 75 per cent of parasite drag and 50 per cent of total normal operating drag. I t has been found by simultaneously considering important aerodynamic characteristics and certain simplified structural criteria that optimum unswept wings at supersonic speeds will be very thin and have very low aspect ratios. As at subsonic speeds, the zero lift (parasite) drag of these wings, as well as that of correspondingly slender bodies, will be composed principally of turbulent skin friction to which Dr. von Karman's work continues to be applicable. Drag due to lift at supersonic speeds is many times that at subsonic speeds, leading to low ratios of lift to drag. Research to improve the drag due to lift at supersonic speeds is greatly needed. Improvements in the lift to drag ratio of wings can be largely reflected in similar improvements in complete airplanes as well. The lower lift to drag ratio, although partially compensated for by better overall power-plant efficiency of turbojet engines at supersonic speeds, leads to much lower range for a supersonic transport. The past record would indicate that marked improvement in range can be expected with continuation of serious efforts in aeronautical research and design. Until considerable improvement in range can be made, the supersonic transport would be subject to the usual complications encountered when operating an airplane over routes requiring important flights longer than the maximum range of the airplane. A simple cost analysis shows that, up to the range attainable by a supersonic transport, there is good hope of retaining operating economy at supersonic speeds near costs attainable with jet transports at high subsonic speeds. This result is possible largely because of the higher speed, tremendous thrust output, and improved overall fuel efficiency of turbojet engines with afterburning. As the speeds of vehicles increase to supersonic and hypersonic levels, their energy becomes very large and predominantly kinetic. In flight near the earth, speed will replace altitude as the major factor insuring effectiveness of action and operating emcienc}^. Range about the earth increases rapidly with speed, but the heating problem becomes very serious. In space flight beyond the earth's atmosphere, the aerodjmamic problems proceed to those of