There is a significant potential for improvements in cruise aerodynamic efficiency of supersonic aircraft through improved design methodology, friction drag reduction, innovative design and the use of favorable interference concepts. The use of favorable aerodynamics concepts such as supersonic biplanes, ring wing, parasol wing and caret wings for the design of a small supersonic aircraft is discussed. The parasol wing concept is shown to offer the greatest potential for improvements in lift/drag ratio relative to a conventional design. However, the best aerodynamic concept is very dependent on the design Mach number, and on the airplane component size relationships. Optimized nacelle installations for a High Speed Civil Transport, HSCT, have aerodynamic interference effects similar to the parasol wing concept.