In recent years, mobile ad-hoc networks have received a great deal of attention in both academia and industry because they provide anytime-anywhere networking services. As wireless networks are rapidly deployed in the future, secure wireless environment will be mandatory. In this paper, we describe a group key management architecture and key agreement protocols for secure communication in mobile ad-hoc wireless networks (MANETs) overseen by Unmanned Aerial Vehicles (UAVs). We use the Implicitly Certified Public Keys method, which reduces the overhead of the certificate validation checking process and improves computational efficiency. The architecture uses a two-layered key management approach, where a group of nodes is divided into: 1) cell groups consisting of ground nodes, and 2) control groups consisting of cell group managers. The chief benefit of this approach is that the effects of a membership change are restricted to the single cell group.