In the last 60 years many new technologies have entered the aerospace industry, but the overall aircraft design remained virtually unchanged. If we compare an aircraft built in the 1960's with the latest generation, they look strikingly similar. Only small evolutionary changes entered the commercial aircraft market. A lot of these changes are driven by the ever-lasting quest to reduce the amount of burned fuel. However, the reduction in fuel usage which can be gained with these small evolutionary changes decreases every aircraft generation. A revolutionary change in the aircraft design is needed to make step-change in aircraft fuel efficiency. Changing the configuration of the aircraft could create opportunities for aerodynamic and structural improvements, which will result in higher fuel efficiency. Current tools used in the field of aircraft design use a lot of empirical data obtained from the analysis of existing aircraft. These tools are not capable of correctly analysing unconventional aircraft configurations. A design tool, called the Initiator, is created which is able to synthesise a conceptual aircraft design based on a given set of top level requirements for a wide range of aircraft configurations including conventional aircraft, canard aircraft, Prandtl-planes and Blended-Wing-Body aircraft. The Initiator is verified by comparing the output of the Initiator with existing aircraft. A selection of thirteen reference aircraft varying from small regional jets to wide-body long-range jet-powered aircraft is made to verify the tool. Top level requirements are defined which match the payload, harmonic range and runway performance specifications of the reference aircraft. The aircraft generated from these top level requirements are compared to the existing aircraft. The design process is proven to work, since it converges to a feasible aircraft design which complies with the top level requirements. By comparing the maximum take-off weights and operational empty weights, it can be shown that the generated aircraft are similar to the reference aircraft. Nine out of the thirteen generated aircraft are estimated to within 10% of the reference aircraft weights. Visual inspection and comparison of external aircraft dimensions show that the implemented design rules are capable of generating an aircraft which is similar to the reference aircraft. The design tool was used to compare the different aircraft configurations. The design process works for conventional, canard, three-surface and Prandtl aircraft. Testing the design process for the Blended-Wing-Body was unfortunately not possible with the current state of the sizing methods. The canard aircraft design results in a 12% reduction in fuel mass and a 28% reduction in operational empty mass in comparison with a conventional aircraft designed for the same payload and harmonic range. However, since none of the analysis methods have been validated the confidence in the results gained from the configuration comparison in low. It can be concluded that the design tool can be used to synthesise and compare a wide range of different aircraft configurations.