In this work, we address the optimization problem of covering a set of mobile sensors with a fleet of flying devices. The goal is to deploy a connected set of Unmanned Aerial Vehicles (UAVs) continuously monitoring the mobile sensors and reporting information to a fixed base station for efficient data collection. We propose an effective optimization model reducing the number of variables of the problem and solved using column generation. Results show that our model is tractable for large topologies with several hundreds of possible 3D locations for the UAVs deployment and provides integer solutions with the generated columns very close to the optimum. Moreover, the deployment changes among time remains low in terms of number of UAVs and cost, to maintain connectivity and minimize the data collection delay to the base station.