| This paper considers a topology construction problem involving a fixed-wing Unmanned Aerial Vehicle (UAV), a set of quad-rotor UAVs and mobile ground users. The constructed topology must maximize the max-min flow rate of ground users over a given planning horizon. To this end, we outline a Mixed Integer Linear Program (MILP) that jointly optimizes the trajectory of the fixed-wing UAV, placement of quad-rotor UAVs, and routing of traffic from each source-destination ground user pair. Solving the MILP is challenging because it requires an exhaustive collection of topologies. To this end, this paper outlines a solution called Rollout to determine the network topology in each time slot of a given planning horizon iteratively. The main idea of Rollout is to generate a sequence of future decisions using a heuristic, where a decision corresponds to the placement of quad-rotor UAVs. Further, each sequence of decisions has a {\em cost-to-go} value. Rollout then selects the sequence with the highest {\em cost-to-go} value. The results show that the max-min flow rate achieved by Rollout is on average $81\%$ that of MILP. |