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The controlled airspace over Switzerland was closed for almost five hours today. How could this happen?
The breakdown: Nothing worked in Swiss air traffic on Wednesday morning. The controlled airspace was completely closed from just before 4 a.m. until 8.30 a.m. Aircraft could no longer take off or land at the major airports in Zurich and Geneva, and overflight traffic was also diverted. According to Skyguide, air traffic safety was guaranteed at all times. A total of around 100 flights had to be canceled or diverted. Thousands of passengers were affected. This major breakdown is a first for Swiss air traffic control.
Certain diverted flights were able to land in Switzerland at EuroAirport Basel-Mulhouse, which is under French air traffic control. Abroad, those airports were used that are closest to the respective destination, such as Frankfurt, Milan, Vienna or Lyon. Basel Airport was also temporarily severely affected. Flights under instrument flight rules (IFR) were not possible at Bern Airport during the breakdown. This includes all scheduled flights. Private flights under visual flight rules, however, were still possible.
From 10 a.m. on Wednesday morning, flight operations were back to 100 percent capacity, according to Zurich Airport. But “we continue to recommend passengers to find out about the status of their flight from their airline,” wrote Switzerland’s largest airport.
Cause: According to Skyguide spokesman Vladi Barrosa, a hardware component in the network failed and had to be replaced accordingly. After a thorough check of the systems, the green light was given at 8:30 a.m. and airspace surveillance was restarted. A cyber attack is definitely excluded. The network error occurred in the Skyguide data center in Geneva and because of the network, the second Skyguide center in Dübendorf was also unable to bridge operations, Skyguide said.
Normally, air traffic control systems must be redundant, ie in the event of a failure, other systems guarantee operation. Skyguide states that the network itself is redundant. “In this case it was a single component that we didn’t have redundantly because that’s not possible. We had to physically swap them out and replace them with a new device,” says Vladi Barrosa. Simply put, a switch didn’t work. This is responsible for data transfer from one computer to another. The second redundant switch, built in as a backup, did not react to this and kept sending the data back.
Consequences: Thousands of passengers stranded at the airports in Geneva and Zurich. According to Zurich Airport, 77 flights had to be canceled there and 15 flights had to land elsewhere. In Geneva, 2,000 people were waiting for their machine. According to the Federal Office for Civil Aviation (Bazl), around 80 flights were diverted. At Swiss, 60 (30 return flights) short-haul flights from Zurich were canceled. Around 6,400 passengers were affected. In Geneva, an additional 8 flights (4 return flights) were canceled, affecting 700 customers. Individual solutions are now being sought for the passengers, Swiss said. According to Swiss spokesman Michael Stief, the airline will cover certain hotel, telephone, transport and catering costs.
According to Skyguide, delays in air traffic can still be expected during the course of the day – especially on long-haul flights. Air traffic is expected to return to normal from Thursday. The Department for the Environment, Transport, Energy and Communications (UVEK) commissioned Skyguide to submit a report detailing the reasons for the closure, the measures taken and an analysis. Politicians are also interested in a review and expect Skyguide to provide clear answers, because everyone is of the opinion: “This shouldn’t happen.”
Costs: Skyguide cannot yet quantify the financial consequences. According to the SRF aviation expert Michael Weinmann, damage in the millions is to be expected. In particular, the outage will result in damage to the reputation of Skyguide. According to Skyguide, the airlines would have to bear the costs themselves. “For the airlines, it’s part of the risk that they have to accept that the airspace can be blocked,” says Vladi Barrosa. Swiss spokesman Michael Stief confirmed that Swiss would not take action against Skyguide: “Skyguide is liable according to the principles of so-called state liability and therefore no recourse is possible.”