Reconfigurable systems are systems that can be transformed into different configurations, to provide different functionality or to adapt to different operating environment. In this paper, we describe the preliminary design process and construction of a first generation modular Unmanned Aerial Vehicle (UAV) that is reconfigurable offline. The modules of this reconfigurable UAV platform can be assembled to form a quad-rotor UAV (QR-UAV) configuration or a fixed-wing UAV (FW-UAV) configuration, respectively providing VTOL/hovering capabilities and long-endurance/range capabilities. The goal of this design effort is to develop, fabricate, and flight-test a modular and reconfigurable UAV platform that can be used by different types of field personnel – from wildfire firefighters, to emergency responders and-post-disaster search and rescue teams. Hence, diverse functionality was deemed necessary along with strict maximum weight/volume specifications (backpack-carry-able modules) and the ability to be assembled/disassembled in a matter of minutes. The overall design and the first generation prototype is derived from an original conceptual design performed using modular product platform planning concepts. The UAV modules were defined in terms of 15 design variables, and the conceptual design optimization was performed using the mixed-discrete Particle Swarm Optimization algorithm. The QR configuration in this UAV comprises four ducted rotors and a central pod housing all the required electronics, including the battery. In addition to all the modules in the QR configuration, the FW configuration includes a multi-section flying wing with vertical and horizontal stabilizers, where the ducted rotors are mounted on the bottom (1st generation concept) or the top (2nd generation concept) of the wing. In developing the detailed design, it was conceived that the majority of the UAV would be fabricated using additive manufacturing techniques. The preliminary design/fabrication/flight-testing processes has now provided us with new constraints that would be implemented in the overall design optimization of the next generation of this reconfigurable UAV platform.