Internal investigation procedure at skyguide

An internal investigation is triggered by an incident, for example a separation minimum infringement at an area control centre. The event is reported by the air traffic controller who observed it, and who then produces an operational internal report (OIR).

The identity of the air traffic controller is confidential, their name is visible only to staff working in the safety department. Skyguide’s investigation division passes all other information in the OIR to the Federal Office for Civil Aviation and the safety investigations body, the Swiss Transportation Safety Investigation Board (STSB).


After receiving the OIR, the investigation division backs up all the necessary data, such as radar, radio and telephone recordings. It then creates transcripts of those recordings, as well as producing explanatory diagrams. These constitute the first information packages sent to the internal units concerned. If, after analysing this initial information, the investigation division or the operational line management reach the conclusion that the case can contribute to the improvement of safety, an internal investigation is launched.


The case is passed to an “ATCO investigator”, an active air traffic controller who has undergone specific training in conducting investigations. This investigator gets in touch with the relevant air traffic controller – if necessary, also with other experts – and conducts interviews relating to the incident under investigation. The aim of these interviews is to obtain information that is not provided by the data hitherto available. The personal opinion of the air traffic controller on the sequence of events during the incident, and on the general situation (weather, traffic volumes, personal feelings and other special factors), is also relevant in order for the case to be understood in its entirety. The ATCO investigator produces an initial analysis on the basis of these findings and the data already available.


Any further procedure will depend on the seriousness of the incident. The following possibilities exist:

  • Share the experience: brief information on the incident is sent to all air traffic controllers in the form of a text or a video
  • Short analysis: a rather more detailed report, but without safety recommendations
  • A full internal investigation using Eurocontrol’s “safety occurrence analysis methodology”


If it is decided to hold a full investigation, the ATCO investigator produces a detailed internal investigation report, which concludes with safety recommendations. Many factors are highlighted in this analysis: organisational factors, environmental conditions, human factors and the lack or failure of safety precautions.


The draft internal investigation report is discussed within the investigation division and is sent to the relevant air traffic controller for information and comment. After this, a final version of the report is received by the unit’s line management, to whom the recommendations are directed. The line management discusses the feasibility of the recommendations, and what action is to be taken, with the unit’s “domain manager safety” and, on the basis of this, the management response is produced. This describes whether, how and within what time horizon, line management is thinking of implementing the safety recommendations. Implementation is then monitored at set intervals.


The investigation report, together with the management response, is published internally as a single document accessible to all employees. The sole purpose of these investigations is always to improve safety. In line with the principles of a Just Culture, no blame is attached or disciplinary action taken, provided that the relevant employees have acted according to the best of their knowledge and belief.