background image

Andreas Fankhauser

5 min Lesezeit

Air traffic controller convictions draw criticism


Air traffic controller and pilot organisations have criticised recent convictions handed down in Switzerland for operational incidents that resulted in neither injury nor damage.

Critics have asserted that criminal prosecutions in the aviation sector tend to do more harm than good and that the sole purpose of safety investigations following aviation incidents is to determine what went wrong in order to use this information to prevent similar incidents happening in future.

Most incidents involve some sort of human error and criminal prosecutions seek to determine who is responsible and punish them accordingly. However, this is contrary to the aims of safety investigations, including learning from past mistakes. There is widespread concern that criminalisation leads to a loss of cooperation from individuals who could provide critical insight into an incident.

This article examines three recent convictions in this context.

Darwin Saab 2000/Sportcruiser incident

In March 2019 the Bulach District Court found an air traffic controller guilty of negligent disruption of public transport within the meaning of Article 237 of the Criminal Code.

This provision penalises with a custodial sentence or a monetary penalty anyone who wilfully or negligently endangers public transport – including air transport – and thereby „causes danger to the life and limb of other people“.(1)

The conviction involved an August 2012 incident at Zurich airport between a Saab 2000 aircraft operated by Darwin Airline and a Sportcruiser-type aircraft that was engaged in flight training.

The controller, who worked for the Swiss air navigation services organisation Skyguide, had cleared the Saab 2000 to take-off from Runway 28 while the Sportcruiser was on short final approach for a touch-and-go landing on Crossing Runway 16. To resolve the potentially critical situation, the Sportcruiser pilots turned away at low altitude. The two aircraft converged to a lateral distance of 205m and an altitude distance of 75 feet.

At the court hearing, the prosecution and the defence disagreed on whether the collision risk had been real or only hypothetical.

Two of the three judges found the prosecution persuasive. As a result, the controller was sentenced to a monetary penalty (the prosecution had asked for a prison sentence, to be suspended pending a probation period).

The defence appealed the judgment.

This conviction followed two convictions in April and December 2018 for similar operational incidents.

Swiss A320/Swiss A320 incident

Another earlier conviction concerned an incident of March 2011 – which also occured at Zurich airport – involving two Airbus A320, each of which were operated by Swiss.

A Skyguide controller cleared the two aircraft to take-off from Crossing Runways 16 and 28. The controller issued the clearances in relatively quick succession. As the two A320 almost simultaneously approached the intersection, one crew aborted the take-off roll and brought their aircraft to a standstill on the runway. The other crew noticed nothing unusual and continued the flight to the destination.

In the subsequent criminal proceedings, the Bulach District Court acquitted the controller of the charges because the collision risk had been insufficiently high.

The prosecution appealed the judgment.

The High Court of the Canton of Zurich reversed. In November 2018 it ruled that the controller was guilty within the meaning of Article 237 of the Criminal Code. It reasoned that the air traffic controller’s conduct had been in breach of relevant regulations and therefore negligent. According to the High Court, this had resulted in a real (ie, not only hypothetical) collision risk; as such, the controller was sentenced to a monetary penalty.

The defence appealed to the Supreme Court.

Ryanair B737/Air Portugal A319 incident

Another earlier conviction concerned the loss of the required separation between a Boeing B737, operated by Ryanair, and an Airbus A319, operated by Air Portugal, while en route under Skyguide’s control in April 2013.

The crew of the Ryanair B737 requested a climb from flight level 360 to flight level 380 due to turbulence, but the crew did not add the call sign RYR 3595 to their request. The controller replied with the instruction to another Ryanair B737 bearing the call sign RYR 6DW to climb to flight level 380. The crew of the first Ryanair B737 then responded with their own call sign RYR 3595 to the instruction to RYR 6DW and began to climb. Neither the controller nor the crew of RYR 6DW responded.

RYR 3995 came as close as 0.8 nautical miles horizontally and 650 feet vertically to the Air Portugal Airbus A319, which had been cruising on a crossing track on flight level 370.

As a result, the on-board traffic alert and collision system TCAS commanded RYR 3595 to descend and the Air Portugal A319 to climb. Both crews immediately followed their TCAS commands and resolved the conflict.

In May 2018 the Federal Criminal Court held that the controller had endangered the life of the passengers and crew of the Air Portugal A319 and the Ryanair B737 RYR 3959. The court found the controller guilty under Article 237 of the Criminal Code and sentenced him to a monetary penalty. The captain of the Ryanair B737 RYR 3959 was found guilty in separate proceedings.

The controller appealed to the Supreme Court.


All of these incidents involved serious operational mistakes on the part of air traffic control. But did these mistakes warrant criminal prosecution and conviction, particularly given that no one was injured and no damage occurred?

The three convictions concluded that a real collision risk had existed which led to a „danger to the life and limb of other people“ within the meaning of Article 237 of the Criminal Code; however, this is problematic.

While Supreme Court case law provides little guidance as to what exactly is required to support such a conclusion in an aviation context, the authorities had made clear that there must be an actual collision risk and not a potential or hypothetical risk. In other words, only residual risk after avoiding action can be considered.

In all three cases, the pilots took avoiding action and quickly resolved a potentially dangerous situation. A realistic assessment should conclude that the residual risk thereafter remained within reasonable bounds.

The better view is therefore that no actual collision risk existed, but it remains to be seen how the Supreme Court and the Zurich High Court will decide in the cases under appeal.

However, as the three cases currently stand, they are testimony to a trend towards criminalisation of aviation incidents and (even more so) accidents. This unfortunate trend may eventually obstruct the influx of safety-related information and, as a result, pose a real threat to aviation safety.


(1) The provision reads:

(1) Any person who wilfully obstructs, disrupts or endangers public traffic, in particular traffic on the roads, on water or in the air and as a result knowingly causes danger to the life and limb of other people is liable to a custodial sentence not exceeding three years or to a monetary penalty. If the offender thus knowingly endangers the life and limb of a large number of people, a custodial sentence of from one to ten years may be imposed. (2) If the person concerned acts through negligence, the penalty is a custodial sentence not exceeding three years or a monetary penalty.

This article was first published by the International Law Office, a premium online legal update service for major companies and law firms worldwide. Register for a free subscription.