Aircraft proximity hazard (airprox)

In accordance with Swiss and international legislation, certain aviation incidents that are associated with air traffic control services have to be reported to the Federal Office of Civil Aviation (FOCA) and to the Swiss Transportation Safety Investigation Board (STSB) using an ATIR (Air Traffic Incident Report) form. Investigating individual incidents is a core task of safety management systems operated by the stakeholders in the civil aviation sector. Serious incidents also have to be investigated by the SAIB.

The International Civil Aviation Organisation (ICAO) defines "airprox" (aircraft proximity) as a situation in which at least one of the involved parties (aircraft crew and air traffic controllers) felt at risk, respectively felt there was a threat to air safety. (...the distance between aircraft as well as their relative positions and speed have been such that the safety (...) may have been compromised).

The term "separation minima infringement" refers to a situation in which the distance that has to be maintained between two aircraft as allocated by air traffic control is shorter than the specified minimum. And the term "inadequate separation" applies in a situation in which no such minimum distance is stipulated and two aircraft come so close to one another that the involved parties cannot rule out the risk of a collision.

If an ATIR should draw attention to the frequent occurrence or typical combinations of potential airprox hazards, the incident is referred to the Airprox Analysis Board (AAB). This interdisciplinary expert group meets several times a year for the following purposes: 

  • To facilitate interdisciplinary cooperation at the national level
  • To exchange different views with respect to potential hazards
  • To formulate joint proposals for recommendations aimed at preventing similar incidents and enhancing the level of safety in the overall Swiss civil aviation system.

Within the AAB, the involved stakeholders make their information and know-how available for the analysis of the various incidents and problems. By taking the findings and measures arising from the individual safety management systems and forming them into an overall picture it is possible to identify patterns and problems at the interfaces (process of hazard identification). 

If a need for action is identified with respect to a given risk potential, in the AAB the required status is jointly defined, together with the desired effects of any necessary measures, and concrete proposals are then made as to how these can be achieved. Such recommendations encompass measures aimed at reducing risks, as well as reinforcing protection factors.

Final reports prepared by the AAB are submitted to the Swiss Air Traffic Controllers Associations (swissATCA) and Swiss Airline Pilots Association (swissALPA) for written comment.

Further information