Airlines and airports rely on the air navigation services (ANS) for the management of air traffic. Hence, ANS provision is considered as a core element for air transportation. Aeronautical information services provide information on the availability of ANS and their associated procedures necessary for the safety, regularity and efficiency of air navigation. Communication facilities have two main categories: aeronautical fixed service and aeronautical mobile service. An ANSP must be able to adjust service provision dynamically to the heterogeneous performance requirements of the airspace users. Moreover, Air Navigation Service Providers after 2010 started forming alliances and cooperating. ANSPs may cooperate for different reason, the most important are: a good cost benefit business case; synergies in technologies and expertise; optimization in the production and achievement of economies of scale or scope; and forced by government regulation or legislation. The chapter also presents an overview on the key concepts discussed in this book.