This thesis investigates the relation between the stiffness of jumping skis and the aerodynamic properties of the flight by using Direct Numerical Simulation (DNS). The majority of previous research exploring the aerodynamics of ski jumping is observational studies. The small proportion of the studies that are simulated do not use DNS because of the high computational cost of this method and therefore cannot accurately describe the aerodynamics. Using the Building Cube Method (BCM) coupled with the Immersed Boundary Method (IBM) allows for DNS to be used in this study. The movements of an actual ski jump are captured via cameras and recreated virtually. This was used as reference for the simulated ski jumps. The results of this study showed a relation between jumping ski stiffness and flight performance, but there were artifacts present in the results. Although one should be wary of drawing conclusions from the results, they do indicate that different degrees of jumping ski stiffness contribute to different flight performance, which means that there might be an optimal jumping ski stiffness for future studies to find.