Thanks to its flexibility and cost-effectiveness, an unmanned aerial vehicle-mounted base station (UAV-BS) is a promising technology for the upcoming 6G wireless networks. Furthermore, tethered UAVs (T-UAVs), which are powered via a tether by an energy source on the ground, can overcome the limited operation time of UAV-BS networks. Hence, T-UAVs sacrifice their mobility and flexibility to maintain long-lasting flight, unlike untethered UAVs (U-UAVs) that can not fly for more than 30 mins. To exploit the best of each type of UAV, the deployment of both T-UAVs and U-UAVs as aerial base stations is investigated. In this paper, we propose a hybrid system composed of tethered and untethered UAVs. We analyze the system by generating Monte Carlo simulations to find a compromise between the two different types of UAVs. Our results prove that for specific cases, the coexistence of tethered and untethered UAVs improves the performance of the system.