Open System Interconnection Reference Model A model providing a standard approach to network design introducing modularity by dividing the complex set of functions into seven more manageable, self-contained, functional layers. By convention these are usually depicted as a vertical stack. Operating Costs The inherent price of producing the output(s), calculated by summing the many individual variable input costs and any fixed internal process costs. Operating Position Work area (workstation) equipped for providing ATC functions. Operational Air Traffic Encompasses all flights which do not comply with the provisions stated for GAT and for which rules and procedures have been specified by appropriate national authorities. Operational Air Traffic (OAT) Flights that do not comply with ICOA air traffic procedures and are therefore subject to military air traffic procedures. Operational Air Traffic Control Used for operations, connected with the operations of ATC. Operational Concept Broad outline of an operational structure able to meet a given set of high level user requirements. It comprises a consistent airspace organisation, general operational procedures and associated operational requirements for system support. Operational Control The exercise of authority over the initiation, continuation, diversion or termination of a flight in the interest of the safety of the aircraft, and the regularity and efficiency of flight. Operational Controller The holder of a certified qualification to permit that individual to control air traffic at a specific operational unit. Operational Coverage Volume The airspace volume defined during the site commissioning of the Radar Sensor and in which radar services can be provided according to the local operational requirements. Operational Database Set of Data used by functions during their operational working service. Some specific data may be modified on-line. Operational Objective Statement of goals to be reached to improve ATM or part thereof. Operational Procedures ATC Operations Manuals, incorporating international, national and local rules and regulations, procedures and working practices. Operational Requirements A stipulated demand placed on someone to fulfil an operational Air Traffic Control / Management need. Instructions which define the opening and closing times of the sectors necessary to guarantee a safe and orderly traffic flow. They are determined by the traffic volume, distribution and complexity. Operational Research The analysis of problems in business and industry involving the construction of models and the application of linear programming, critical path analysis and other quantitative techniques.

 
Operational Response The Operational Response is the end result, generally of an operational nature, expected by the originator of a data link transmission. The Operational Response can be human or system generated. The Operational Response indicates to the sender of an operational transmission, such as a request or instruction, the operational action taken as a result of it (e.g. request or instruction). Due to its operational content and meaning, an Operational Response is a higher level response in comparison to a Logical Response. An Operational Response may be followed by one Logical Response and/or another Operational Response. Operational Response Time-out The Operational Response time-out, represented as (to) in the Time Sequence Diagrams, is the maximum end-to-end time allowed from the moment the triggering event is issued from the originator user process and the moment the operational response is delivered to the originator user process. It therefore includes: the technical data extraction and composition of the data message which requires an Operational Response; the data transmission and processing; the waiting time for the operator’s response action, if applicable; the transmission and receipt of an Operational Response. Operational Service and Environment Description It is part of the methodology developed by EUROCAE WG53 for the approval of data link services and is described in ED78A. Operational Significance Information essential for the safe and efficient conduct of a flight. Operational Staff The staff working in the operational environment of ATS comprising ATCOs, flight data assistants, flow managers, operations room supervisors and ATS support staff. Operational Training Training given in the operational work situation and following institutional training. It comprises transition training, pre-OJT and OJT. Operator A generic human operator interacting with the FDPS. Specialised in various roles such as controller, supervisor, flight data assistant, etc. Optimisation Strategy (AMAN) is a method to obtain the balance between maximising benefits and minimising (disbenefits/shortcomings) relating to efficiency, capacity and safety. Different AAF may have their own benefit profiles. Optimised Sequence A sequence of arriving flights calculated based on constraints at the constraint point and optimisation criteria. Orbital Holding An aircraft flying a "racetrack" pattern based on a defined constraint point. Ordinal Scale A scale in which it is possible to rank or order all categories according to some criterion. Organisation Abbreviated form frequently used for the Eurocontrol Organisation (i.e. Member States and the Agency).