During the last four or five years a remarkable evolution has taken place in the policy of aircraft design. Its ultimate aim is to reduce the aeroplane to the simplest possible form offering the least resistance to the air. This process of eliminating any structural members which are not necessary for the production of lift and the housing of passengers or military load has automatically led to the adaptation of the fully cantilever monoplane with retractable undercarriage (Fig. I). The final logical result of this evolution is, of course, the flying wing with the engines, passengers or military load housed inside, thus suppressing such components like the fuselage and the tail unit which at the moment are still causing a non-productive addition to the total drag. There are still certain difficulties which will prevent us from achieving the ideal of, say, a mere flying wing, and our present compromise solution consisting of a tapered cantilever wing, a streamlined fuselage and a cantilever tail unit will probably persist for some time to come. The next step in suppressing parasitic drag will, therefore, consist in a still greater refinement of fuselage design and in eliminating outside engine nacelles by using engines buried inside the wing.