The Large Passenger Aircraft (LPA) Platform 2 – Multifunctional Fuselage Demonstrator (MFFD) will employ new combinations of airframe structures, cabin/cargo, and system elements using advanced materials, notably HPTP composites. The MFFD is focused on achieving significant cost and weight reductions, coupled with high production rates. To bring these materials to market, there is a need to validate direct joining methods, which eschew traditional adhesive bonding in order to reduce cycle time and improve joint quality. The MECATESTERS project represents a key step in the progression of such technologies to widespread use in the aerospace sector. It will permit a greater level of understanding of the micro-mechanical behavior of the interfaces – an understanding which is currently limited: issues such as aging, healing, processing parameters, and durability need to be investigated in greater detail in order to develop a coherent approach. The MECATESTERS project will elucidate many aspects of thermoplastic joining using precision thermoplastic welding (PTW) methods. It will examine systematically the effects of surface condition, matrix aging, and bonding method on the reliability and performance of assemblies bonded using a variety of thermoplastic welding technologies.