What happens, when ATC makes a Mistake?

Small Mistake, Big Consequences

What happens when an Air Traffic Controller makes a mistake? It’s a big question because at the end of the day the life and safety of passengers and crew don’t just depend on the plane and the pilots but also the judgment of well trained ATC staff in towers, control centers, etc. all over the world.

Examples from the past show what can happen when ATC makes a mistake. In 2002, Bashkirian Airlines Flight 2937, a Tupolev Tu-154 passenger jet, and DHL Flight 611, a Boeing 757 cargo jet, collided over Germany resulting in the death of 71 people. There have been several court cases where individual employees of the Air Traffic Authority have been sentenced to imprisonment, suspended sentences, and fines.

But what happens, if ATC makes a mistake, where nobody was hurt? What is the call to make in such a case? Does there have to be an internal investigation? Does the controller need to be dismissed? Or should he even be brought before a court?

The Incident

April 2013. A Ryanair flight from Pisa (Italy) to Lübeck (Germany) and a TAP flight from Lissabon (Portugal) to Prague (Czechia) both just entered Swiss airspace. They both contacted Center Control where an Air Traffic Controller of the Swiss ATC department “SkyGuide” was in charge of handling all traffic in the area. It was just a regular day; nothing special happened so far.

At one point, the Ryanair pilot asked for an altitude change. Nothing out of the ordinary, however, he only reported the callsign, but not the flight number. The air traffic controller thought the request came from another Ryanair aircraft and allowed the change of altitude without a concrete demand for the specific callsign. The Ryanair pilot from whom the request came thanked, again without naming the callsign.

During the climb, a TCAS alarm suddenly sounded in the cockpit of the Ryanair aircraft. The aircraft came dangerously close to the TAP flight. The smallest distance between the two aircraft was 1.5 kilometers horizontally and 198 meters vertically. The prescribed minimum distance was 9.26 kilometers horizontally and about 305 meters vertically.

The error was noticed; the planes were able to avoid and continue their flight safely. People were not harmed — a mistake without damage.


The Aftermath
Last May, the Swiss Federal Criminal Court sentenced the air traffic controller to a conditional fine of 60 daily rates at 300 francs. The ATC controller lodged an appeal with the Swiss Federal Supreme Court against this first-instance decision. However, the appeal was rejected on Thursday.

In its ruling, the Federal Supreme Court states that the air traffic controller has created a real threat and violated his duty of care. The convicted person, on the other hand, argued that there had never been a real danger because the trajectories of the two aircraft involved had not crossed. However, the Federal Court does not accept this argument because unexpected influences are also to be expected.

The verdict has caused considerable uncertainty among air traffic controllers. A good dozen air traffic controllers had called in sick or unable to work today, a Skyguide spokesperson said.

In addition, the number of voluntary reports which air traffic controllers can file after a mistake in order to analyze the error and avoid it in the future has fallen sharply following the first instance ruling in May. The controllers are afraid to say too much because one fears that what has been said can be used against them. According to the SkyGuide spokeswoman, the verdict against the air traffic controller would have had the opposite effect because of this. Safety would suffer as a result.

What do you think?
What’s your opinion on that? Mistakes can happen, as long as there is no harm? Do you believe that the ruling of the court is fair?

In my opinion, it is essential to analyze mistakes in order to learn from them. I also think it is right to take internal disciplinary action if an air traffic controller has been extremely negligent. However, I believe it is wrong to bring an air traffic controller before a court and convict him for a mistake in which no one has been injured and in which gross negligence is only present to a limited extent. All the other air traffic controllers are made to feel insecure, and safety ultimately suffers as a result.

Thank you, and happy landings!

Sources (German)


From personal experience, we have an open, honest reporting policy in the UK where an error that does not result in loss of human life or equipment results in an investigation without blame.

This creates an environment where controllers are willing to report on themselves and one another without putting themselves or others “under the bus”.


And that’s exactly how it should work, in my opinion. As I said, a court decision like that only has the opposite effect. Errors are no longer reported or only half-heartedly, processes can only be optimized with difficulty, security suffers.

I think that Switzerland must now think about how to defuse the situation. For example, people are already talking about a new law that could remedy the situation. Let’s see what happens.


Impossible to go to solo mode

That’s definitely the way to go.

Figuring out from whence errors stem and learning from them is a lot more productive than fining one guy 3 months’ salary.


Just had to say I love your post.IMO it is very informative, and interesting and educational. Thanks, it made me scratch my head too about when I make a mistake on the sim.


ATC is one of those niche areas where there’s generally a poor understanding of the nuances involved when your standard-fare courts get involved. Not to ding on those who don’t have a grip, especially given how specific this type of work is as previously mentioned, but the internal metrics of ATC operations seems not to have been weighed here.

Callsign confusions are fairly common all over the world; the supposition here seems to lay on blame being shared by both the pilot and controller. Yet, the controller by measure of a court who is not versed in the dozens of factors leading up to this situation, is deemed guility. Most unfortunate.

Here in the U.S, the FAA takes charge of and investigates aviation incidents such as this one. As a governmental body dedicated solely to those type of things, their word is far more accepted and has meaning to those involved.

In short, it’s a messy situation.


Sorry Ryanair pilot where was your situational awareness in this moment?

I clearly get my surrounding traffic indicated and when I request a FL , ALT or HDG change I first look what’s around me and even if I get the permission I don’t just climb or turn and close my eyes waiting for TCAS resolution.

Yes ATC was sleeping but there are always more then one person involved until TCAS is shouting to you.

When we are enroute and request a level change or “req. heading 123 due to weather “ we first look around and especially when it comes to an altitude change we discuss the situation before like “ ABC center, LH 061 request climb FL350 behind Air France 123 ( or after passing a waypoint when we are clear of traffic ).

That gives the controller the picture that we actually monitor the traffic around us and also we can offer a climb rate of let’s say 300 until clear of traffic …



I mean the pilot is hardly in the clear in my mind. I don’t think incidents like that should be persecuted, it creates a bit of a culture of fear I think oposite to what @Mags885 is saying where people are afraid to report something, or ask a supervisor/higher up to help/change something for the better since all incidents and mistakes are under the microscope. Now don’t mistake me for saying all should be forgiven in all circumstances. These people have important jobs, and there should absolutely be accountability, but I think sometimes a near miss is almost punishment enough. Like that controller will always ask for a full call sighn now I’d be willing to bet, and the Ryan air pilot will always give his. Now learning by mistakes is hardly something that should be encouraged in these jobs, but when a mistake is made they will learn. That is sum what unfortunately why aviation is so safe because it’s really good at not repeating mistakes…

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If it results in no deaths they will put them on a breathalyzer and if it results are positive the pilots and passengers can Persecute. That is why it is a big deal to have a great Aviational attorney

I believe the decision of the courts has definitely degraded the safety culture that would be present in the organization, as evident by the lack of safety reporting being conducted now. Assuming that the controller did not do this out of negligence, I don’t believe there should be any court cases or convictions taken place but as you said rather internal disciplinary actions taken.

From the sounds of it, the company should revisit, or if non-existent, instate their own ICAO SMS program to help and mitigate any further potential risks such as this. Although that would not 100% prevent any further incidents from occurring, it would help promote a better safety culture, and would find common trends in errors, which leads to a safer industry for everyone involved.

If only us Americans weren’t so stuck up 😂

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So what was the read back of the controller? Did he also just mentioned “ Ryanair climb/ descent FL… “ or did he say “ Ryanair 123 “ climb/ descent FL …” ? If the controller used the flight number of the other Ryanair aircraft which he thought the request came from and gave him the permission then the Ryanair plane from which the request originally came climbed/ descended without permission.

Even i wonder what kind of reporting system Skyguide uses…We have a system called Confidential Safety Report and on this report you find the following, important note :

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For all that ATC does we don’t get enough credit

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