A design method is presented that has been implemented in a software program to investigate the merits of conventional and unconventional transport airplanes. Design and analysis methods are implemented in a design tool capable of creating a conceptual design based on a set of toplevel requirements. In contrast to established design methods, emphasis is placed on designing unconventional as well as conventional airplane configurations. A parametric fuselage primitive and a parametric lifting-surface primitive have been defined. By combining various instances of these primitives, airplane geometries ranging from blended-wing-body configurations to threesurface configurations can quickly be generated. Analysis methods have been developed/refined such as to enable the (physics-based) disciplinary analysis of conventional and unconventional airplane concepts. Design rules have been implemented to automatically size the main airplane components. This paper describes the workings of the software tool, presents relevant validation studies and showcases a comparison study between five different airplane configurations.