There is a growing attraction for robotic aerial systems in the academic world and in industry. Aerial Cable Towed Systems (ACTSs) are naturally subjected to various unknown external actions (wind, human, etc.). Accordingly, it is crucial to characterize their stiffness both for balancing external disturbances and for their design. Thus, in this paper, an ACTS with a point-mass end-effector, subjected to a generic force, is considered. The effect of the number of cables and the cable arrangement on the stiffness of the ACTSs is investigated. It turns out that the cable arrangement is the factor that enhances most the stiffness of the ACTSs.