This study reports the formulation of a realistic aircraft wing model based on thin-walled composite beam theory. In this model, NACA 4-digit-series airfoils were selected for the wing-section. The circumferentially asymmetric stiffness lay-up was implemented and two different sets of coupling systems corresponding to the proposed model were utilized. The eigenvalue problem was solved by the extended Galerkin method and the natural frequencies were computed as a function of the ply angle. The results of the free vibration analysis along with the governing system of the proposed model contributes to the theory of anisotropic thin-walled beams, emphasizing the importance of thin-walled structures in the design of advanced aeronautical structures.