Probable Positions (MTCD)
The probable positions (MTCD) of a flight at a certain moment in time are all positions within the uncertainty areas (MTCD) of the flight.
Problematic Use of substances
The use of one or more psychoactive substances by aviation personnel in a way that : a) constitutes a direct hazard to the user or endangers the lives, health or welfare of others; and/or b) causes or worsens an occupational, social, mental or physical problem or disorder.
Procedure and Working Instructions
1- How something is accomplished. (Source: James Martin, Information Engineering 1990);
2- A method by which one or more processes can be carried out. (Source: James Martin,
Information Engineering 1990);

3- A sequence of detailed instructions that performs specific physical tasks to support a process. (Source : James Martin, Information Engineering 1990).
Procedures For Air Navigation Services
An ICAO term preceding another term such as RAC for Rules of the Air and Air Traffic Services and OPS for Aircraft Operations which are publications issued by ICAO. Two other titles complete the PANS series, they are ICAO Abbreviations and codes and Regional Supplementary procedures.
Process
1- Set of inter-related resources and activities which transform inputs into outputs. (Source: ISO 8402-1994).
2- An activity that starts and stops, and is executed repeatedly. Processes are determined by successively decomposing the business functions. The word process relates to what is being done but not how it is done. (Source: James Martin, Information Engineering 1990).
3- Processes can be decomposed into processes and are triggered by an event and carried out by a business segment to achieve a stated purpose. (Source : James Martin, Information Engineering 1990).
4- A series of events, actions, operations,
communications, and changing relationships in a situation.

5- A series of logical and normally sequential actions which result in the transformation of an item from one state to another or some development.
A series of logical and normally sequential actions, which result in the transformation of an item from one state to another or some development.
Process Control System
One of the four components of the structural model of cognitive processes of ATC. Internal evaluation system which makes sure that action takes place as planned by the controllers.

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Processing
The examination of NOTAM received from other NOF in order to verify suitability for acceptance into an automated AIS system, undertaking conversion, translation, syntax correction, data correction, editing and/or summarising as required.
Professional Development
The systematic maintenance, improvement and broadening of knowledge and skill together with the development of personal qualities necessary for the execution of professional, managerial and technical duties.