The number of aircraft equipped with broadband connectivity is increasing. With several hundred users per aircraft, a high capacity air-to-ground link needs to be ensured. Today, several systems provide connectivity to aircraft. However, these systems are not optimized for changing aircraft densities in different geographical areas and thus the actual throughput per aircraft varies during the flight. Therefore, we investigate the achievable throughput during any given flight by analyzing actual flight routes in order to determine the relevant parameters to satisfy current and future connectivity needs. We show that multiple air-to-ground communication systems need to be exploited to offer sufficient throughput to all aircraft.