In the last years, the increasing cost of fuel and the need for a reduction in air traffic pollution has led civil aviation to move its attention toward the construction of more efficient aircraft. In order to achieve this goal, the aeronautic industries have usually tried to improve aerodynamics and to build lighter structures but, recently several solutions have been proposed in order to lead a radical change in the standard aircraft configuration. This thesis aims to examine the configuration called PrandtlPlane, the task is to optimize the wing structure of a non conventional ULM starting from a PrandtlPlane prototype. The first part of this manuscript gives an introduction about the main features of a PrandtlPlane aircraft. The second part depicts all the features of the prototype, while the third ones aims to the describe the design process and how it is implemented. Finally, in the last part of this job the results of the design process will be verified through a finite element analysis. The analysis done allows a comparison between the prototype and the new structure, and shows how the PrandtlPlane configuration provides higher performance than conventional structures.