Abstarct: Nowadays, aeroelasticity is considered one of the significant branches within aerospace engineering. The role and importance of issues related to this field have reached a level where conducting aeroelastic analyses and ensuring compliance with aeroelastic margins are regarded as essential stages in the design of flying vehicles. Various software tools have been developed for this purpose. Given the increasing demand for the use of composite materials in aerospace structures, it becomes imperative to investigate the effects of various parameters, including fiber orientations and the laminate stacking sequences of composite materials, on the boundaries of aeroelastic instability (flutter and divergence) in composite aircraft structures. A cantilever beam made of non-isotropic materials with a closed cross-section and thin walls has been modeled, taking into account the effects of shear deformations, as well as primary and secondary warping. Additionally, unsteady aerodynamic loads have been transformed into state-space form. Due to the inherent non-conservative nature of the problem, classical modal analysis methods for solving eigenvalue/boundary value problems are not applicable. To form the mass, stiffness, and damping matrices of the non-conservative aeroelastic system, variable separation and Galerkin methods have been employed. Ultimately, by transforming the matrices into state-space form, eigenvalue analysis for aeroelastic stability assessment was conducted.