This paper describes a novel Nonlinear Internal Model Control (NLIMC) approach. We show that if we change, in a new manner, the control based on flatness property in order to get a closed loop structure, we can raise the performance and the robustness level with regards to structured or unstructured disturbances. The control performance is evaluated through a Vertical Take-Off and Landing (VTOL) Unmanned Aerial Vehicle (UAV) where numerical simulations are performed demonstrating the effectiveness of this novel controller form. The obtained results are confirmed by series of experimental tests showing also the robustness level of this technique in presence of wind.