Task was to find an innovative aircraft design for a new medium range aircraft. The aircraft design methodology is based on equations (in contrast to numeric methods) and formal optimization with a genetic algorithm called differential evolution. Airbus has postponed an all-new A320 to 2025 or even 2030. This allows including also unconventional configurations into the search. Economic requirements are extreme: 25 % to 40 % reduction in fuel consumption, 35 % reduction in Cash Operating Costs. To achieve this, all aircraft design parameters have to be open for discussion. An aircraft called "The Rebel" is prepared to go to extreme parameters: low cruise speed, high wing span and long take-off and landing distance. Without new technologies it achieves 36 % reduced fuel consumption. The "Smart Turboprop" stays in conventional limits with its parameters, but makes use of a braced wing with natural laminar flow. It also achieves 36 % reduced fuel consumption plus a 17 % reduction in Direct Operating Costs (DOC). In addition, several Box Wing Aircraft where designed: Diamond Box Wing and Biplane Box Wing as Wide Body and alternatively as Slender Body. The Biplane Box Wing shows overall advantages due to its conventional tail. The details of Box Wing Aircraft design where mastered, but the Direct Operating Costs of the Box Wing Aircraft turned out to be higher than those of the A320 reference. This leaves the "Smart Turboprop" as the proposed configuration for an Airbus A320 replacement. As a short term measure, it is proposed to offer a horizontal wing tip extension as an option for the A320neo instead of the winglets. An extension with the same length as the winglet height offers far greater drag reduction. Airports will tolerate and accommodate some aircraft with a wing span above the ICAO limit in Class C of 36 m.

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