This circular provides a more detailed view of the air traffic management service delivery management (ATM SDM) component of the Global Air Traffic Management Operational Concept (GATMOC, Doc 9854) — a component that is of chief importance because of its coordinating role. Even if more detailed, this view is still at the same conceptual level as the GATMOC itself and hence an integral part of it. It is foreseen that the material in this circular will be incorporated into Doc 9854 in the future.