A body configuration for improving the fluid-dynamic performance efficiency of aircraft and watercraft comprises a generally conical upper segment (54) and a generally conical lower segment (56) that are joined at a common base plane (53), achieved by inverting the conical lower segment (56). The slopes of the conical surfaces are determined by the prescribed planform of the craft or vehicle and by the height of the conical segments wherein the height of the conical upper segment (h.sub.u) is less than and typically two-thirds that of the conical lower segment (h.sub.L). Although not limited to elliptical planforms, a generally circular planform (52) is preferred for a vertical takeoff and landing aircraft operating in the subsonic flight regime and an elliptical planform (68), with a large aspect ratio for takeoff and low-speed flight, then rotating to a low-aspect-ratio orientation for supersonic flight operation, is preferred for supersonic transport and single-stage-to-orbit type aircraft. The unique conical configuration allows the aircraft to take off and operate at low-speeds with the high lift and efficiency of the large aspect ratio orientation, operate as an oblique all-wing aircraft during climb and acceleration to higher flight speeds, and then fully transition to the low aspect ratio orientation for high-speed operation, including transonic, supersonic, and hypersonic flight. Allowable modifications are defined to optimize and adapt the universal fluid-dynamic body to satisfy unique functional requirements of potential vehicle applications, including submersible and surface-effects type watercraft.