The International Civil Aviation Organization (ICAO) has defined a mobile IPv6-based aeronautical telecommunications network (ATN/IPS) as a next generation communication network for future air traffic management (ATM). The ATN/IPS will be used with different terrestrial and satellite link technologies for supporting future ATM. In parallel, non-operational services will use different link technologies as well. In such an environment, the main challenge is to design a network architecture that integrates all link technologies in a way that mobile users (be it a cockpit user or a passenger) can make use of them in a seamless way. This paper presents the core functionalities developed within the NEWSKY project of such an integrated IP network architecture.