The purpose of the work described in this book is to verify with a FEM analysis a preliminary design of the wing structure of a 250 seats PrandtlPlane aircraft, made up in aluminum alloy. The wing structure has been optimized with a multistep process. Moreover, a composite design of the structure is here investigated, with a preliminary sizing of the wing and a FEM analysis of the system together with the buckling analysis of the compressed skins is accomplished. The results in terms of weight and stress distribution are shown, and a comparison between the metal and the composite solution is performed.