The unsteady vortex method has been extended to account for blade flexibility and tower interference. These are two potential sources of unsteadiness of the flow past a wind turbine blade. The cases presented correspond to an incoming flow speed V = 5 m/s and low yaw angles and V = 8, 10, and 12 m/s and zero yaw. Comparisons of the root flap bending moments predicted by the model with the National Renewable Energy Laboratory (NREL) experimental data indicate that the NREL blades designed for the wind tunnel campaigns are quite rigid and that the tower interference is responsible for unsteadiness that is well captured by the model for zero yaw as well as for yaw of 5, 10 and 20 deg.