Flutter instability of symmetrically laminated anisotropic composite flat panels exposed to a coplanar supersonic flow of arbitrary direction is analysed Due to the complexity of the problem, the solution is obtained via the Rayleigh-Ritz procedure generalized to the case of non-conservative systems. Towards the same goal, the concept of the stability parabola coupled with Sylvester's determinant technique are used to determine the flutter boundary. The structural plate model incorporates the effects of transverse shear as well as the material anisotropy and heterogeneity while the aerodynamic loads are expressed in terms of the supersonic quasi-steady 2-dimensional approximation. The numerical results underline the strong influence played by transverse shear, as well as the inadequacy of the classical Kirchhoff model when applied to a panel which does not fulfil the requirements of a thin plate and/or when its material exhibits a weak rigidity in transverse shear