Summary: The aerodynamic performance of twin NACA0012 flapping wings is investigated for different combinations of sinusoidal plunge and pitching motions employing Reynolds Averaged Navier-Stokes approach on moving and deforming hybrid grids. The results show that better aerodynamic performance of flapping wings can be obtained at relatively low flow speed for symmetric wings, while both lift and thrust decrease with the amplitude of the plunge and the pitching motion for non-symmetric wings at high speed.