The increasing use of unmanned vehicles in civilian (metropolitan traffic monitoring, rapid assessment of disaster areas) and military (reconnaissance, target identification, tracking and engagement) domains has driven critical requirements for the interoperability of manned-unmanned systems. In this work, we provide the design and the development of a flight mission simulator structured for joint real-time simulation across manned-unmanned fleets, and the mission control center. The hardware structure within the network simulator is tailored to mimic the distributed nature of each of the vehicle's processors and communication modules. Open-source flight simulation software, FlightGear, is modified for networked operations and it is used as the 3D visualization element for the pilot and the mission controls. The UAV dynamics and low-level control algorithms are embedded within the xPC target, computers. Equipped with 3D flight simulation displays and touch-screen C2 interface at the desktop pilot level, the platform also allows us to rapidly prototype and test pilot-unmanned fleet supervisory control and pursuit-evasion game designs. In addition, the unique design enables seamless integration of real unmanned air vehicles within a simulated scenario. Hardware-in-the-loop testing of network bus compatible mission computers and avionics systems provides its with validation of the C2 architectures and the hardware designs on it realistic lab-scale platform before the actual flight experiments.