Uninhabited combat aerial vehicles (UCAVs) are intended for carrying out high-risk combat missions with a high degree of precision, effectiveness and efficiency and without endangering pilots’ lives. An air refuelling system for UCAVs could bring out their full potential in wartime action, by extending their range capability and increasing their airborne time. Hence, the main aim of this PhD research programme was to develop a design and optimisation methodology for an innovative concept consisting of a large uninhabited tanker and a number of UCAVs flying in a close formation, with an optimised and fully autonomous air refuelling capability. The close formation flight of this tanker and UCAVs combination provides aerodynamic benefits which together with an optimised air-to-air refuelling sequence will result in a significantly extended combat radius and capability without unnecessarily compromising the UCAVs’ physical size. With a stealth design approach, the proposed combination could fly directly to a faraway destination without any intermediate stops, hence minimizing any risk of detection, with significant fuel and time savings. To fully exploit the potential advantages the above combination, both the autonomous tanker and the UCAV concepts have been designed through specially developed and separate synthesis methodologies and each aircraft was subsequently optimised for its respective operational role. An investigation into formation flight aerodynamics has also been conducted. A method for evaluating the associated aerodynamic benefits has been developed using a modified vortex-lattice approach, to automatically locate an optimal formation position for each aircraft in flight. A further method has also been developed to optimise the air refuelling sequence of the UCAVs by utilising the design synthesis and formation flight results aiming to maximise a range objective function. The above design synthesis and optimisation methodologies have all been integrated into an automated program written in Visual Basic.NET, featuring Graphical User Interfaces for simpler, faster and repetitive implementation.