AATMS (Airborne Air Traffic Management System) aims to bring the European avionics (aircraft electronics) industry a big share of the on-board telematics equipment market for the air traffic management and control of the future. For the European avionics industry, the capability to develop an on-board architecture for the future Communications, Navigation and Surveillance/Air Trafic Management (CNS/ATM) environment is of strategic importance, being the focal point of future on-board systems and therefore dominating cockpit avionics. Therefore, AATMS should help the European avionics industry to obtain a significant market share. In the course of the project, a demonstrator for an AATMS was developed and evaluated. The work focused on data link realisation and communication management and onboard CNS/ATM functions that are compatible with the future European air traffic environment, including flight plan negotiation and 4D planning/guidance.