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17 July 2019 Conviction of air traffic controller

A critical look at BGer 6B_1220/2018 of 27 June 2019 (Skyguide)

In its ruling of 27 June 2019, the Federal Supreme Court confirmed the decision of the Federal Criminal Court in Bellinzona to convict a Skyguide air traffic controller for negligent disruption of public transport. The ruling has already provoked strong reactions, particularly from air traffic control. As a result, it is doubtful whether it will contribute to the safety culture in aviation ("just culture").

1. Initial position

The judgment concerns an incident of 12 April 2013 in which two Ryanair aircraft were confused and, as a result, there was a close call (Airprox) in Swiss airspace between a Boeing 737 of the Irish airline Ryanair and an Airbus A319 of the Portuguese airline TAP.

Due to expected turbulence, the pilot of a Ryanair-Boeing 737 asked the tower to be allowed to climb to a different altitude without giving their radio call sign. The air traffic controller did not enquire who was making the request and gave the permission to climb, but mistakenly to the pilot of another Ryanair aircraft in the same sector who ignored the clearance. Subsequently, the first Ryanair pilot, who had made the request but had not received clearance, initiated the climb of the Boeing – this action was punished by the Office of the Attorney General of Switzerland on 4 April 2017 with a penalty order for negligent disruption of public transport. The machines came too close to each other and shortly afterwards, the conflict warning system on the ground triggered an evasive order, which the two pilots of the TAP-Airbus and the Ryanair-Boeing immediately followed. The smallest distance between the aircraft was 1.5 kilometres horizontally and 198 metres vertically. The prescribed minimum distance is 9.26 kilometres horizontally and 304.80 metres vertically.

2. Federal judicial considerations

With its decision, the Federal Supreme Court confirmed the ruling of the lower instance. The Federal Criminal Court (judgment SK.2018.1 of 30 May 2018) had previously sentenced the air traffic controller to a conditional penalty of 60 daily penalty units of CHF 300 each for a probationary period of two years for negligent disruption of public transport within the meaning of art. 237 para. 2 of the Swiss Criminal Code (SCC).

In its judgment, the Federal Supreme Court states that the air traffic controller's conduct violated his duty of care and thus created a concrete threat. In particular because air traffic controllers have a specific control function which means that they have to anticipate mistakes made by others.

Whether there was a specific risk in the legal sense must be decided on the basis of an assessment of the facts. According to the Federal Supreme Court, a clear indication of a concrete hazard was the fact that the prescribed safety distance between the two machines had been massively undercut and as a result an evasive manoeuvre was necessary. The Federal Supreme Court did not accept the argument of the defence that there had never been a concrete danger at any time because the trajectories of the two aircraft had not crossed (even without evasive manoeuvres). The Federal Supreme Court explained that external factors influencing air traffic must always be taken into account and that the minimum vertical and horizontal distances must therefore be observed.

The present judgment also failed to take into account the argument that all aircraft in circulation today are equipped with conflict warning systems and that human error can thus be corrected.

3. Commentary

The present Federal Supreme Court ruling could have far-reaching consequences for the safety culture in aviation. As far as can be seen, this is the first legally binding criminal conviction of an air traffic controller in Switzerland.

It is questionable, in particular, whether the open culture of error (known as "just culture") that has hitherto been practiced in air navigation services both internationally and nationally (not only by Skyguide, but also by airlines such as Swiss and Zurich Airport) can be maintained. This system enables aviation staff to report errors and incidents without fear of criminal or disciplinary consequences, provided they have not been committed with gross negligence or even intentionally, and to participate as impartially and completely as possible in the clarification of the facts of the case. The Federal Supreme Court, on the other hand, apparently does not want to concede any human error to air traffic controllers. The signal sent out by the criminalisation of such behaviour does not promote the improvement of safety in air transport.

It should also be critically evaluated that the lower court, when assessing the actual risk of collision, relied solely on the analysis of the Swiss Transportation Safety Investigation Board (STSB) instead of having this question clarified by an expert in the light of criminal procedural law. The problem here is that questions of guilt and liability are not the subject of the investigation of the STSB and should therefore not be based solely on these findings in judicial proceedings in the context of the investigation of the facts. The purpose of a STSB report is rather to gain knowledge which can be used to prevent future accidents and hazardous situations and thus increase safety in air traffic in general. There is a danger that criminal procedural principles, in particular the prohibition of self-incrimination, will be rendered null and void if the persons concerned contribute to clarifying the facts before the STSB and these findings then reach the public prosecutor's office without further process.

By classifying the unexpected (additional risk-increasing circumstances, failure of all other security mechanisms) as expectable at the expense of the air traffic controller, the Federal Supreme Court ultimately turns a concrete dangerous offence such as art. 237 SCC into an abstract one. The fact that the air traffic controller is only one link in the necessarily and deliberately multi-level safety chain in aviation is ignored. It seems unsatisfactory that slight or simple negligence should lead to a criminal conviction of the air traffic controller in the case of a technically corrected (if at all likely) "concrete" hazard without any personal injury or damage to property. Of course, events like Überlingen 2002 should not occur in the first place. However, criminal law must remain the ultima ratio of the rule of law. Apart from gross negligence and intent, in cases such as this the focus should be on improving safety in aviation.

A reduction in the general capacity bottlenecks in the Swiss and European air traffic infrastructure, for example at Zurich Airport, or the further implementation of the Single European Sky (SES) would promote security. In addition, there has already been a call for the legislator to take account of the principle of just culture. Skyguide itself should at best be held responsible for the (non-gross) negligent actions of air traffic controllers. It is also to be expected that, as announced, Skyguide will make full use of or even increase the available safety margins.

It remains to be seen what further developments there will be, both in the upcoming busy summer holiday months and in federal Berne.

Our Transport/Aviation Team will be happy to answer any questions you might have.

Authors: Urs Haegi, Peter Kühn