One of the challenges in Multidisciplinary Design Analysis and Optimization is raised by the fidelity of the methods and tools used within each single discipline. This element, introducing uncertainty in predictions, is neglected generally. In this work, a framework is built to analyse the impact that the fidelity of the aerodynamic model has on four key figures of merit, including Maximum Takeoff Weight, maximum Lift-to-drag ratio, fuel weight and takeoff length. It is found that the aircraft configuration with minimum fuel weight computed with two aerodynamic models differs significantly, with large variations in terms of predicted fuel weight and wing planform.