The European Commission has launched numerous initiatives to develop advanced concepts, assistance tools, technologies to support the planning and execution of air traffic management (ATM) tasks, and to cope with the high growth rates in air traffic demand. It is generally recognised that, before any implementation, it is necessary to assess the validity of these concepts, validate the specifications of the tools and to demonstrate the feasibility of the technologies. This work is particularly needed because all these advanced features will be developed in a distributed framework by different teams. The validation activities lead to a strong need for the use of testbeds.