Europe’s air travel chaos spread to Switzerland on Wednesday after a technical malfunction at the country’s air traffic control system shut down flights nationwide and left thousands stranded across the continent. 

Swiss airspace was closed around 6:30 a.m. and remained so for roughly two hours. Zurich Airport said flights gradually returned to normal operating capacity as of 10 a.m. The closure caused widespread delays that still persisted later Wednesday morning, European airspace manager Eurocontrol said.

Tension was high at the Zurich airport as hundreds of frustrated and confused travelers tried to rebook flights, obtain reimbursements or get access to lounges. Some travelers bought new tickets or rebooked to travel a day later, only to learn there were still open seats to travel on Wednesday.

Mina Israil, a 29 year-old sales manager who was meant to fly to Paris for a business meeting at noon, managed to organize a flight later Wednesday but wasn’t offered any compensation. 

“I frequently fly through Zurich and this is the first time something like this happened,” Israil said. “It’s a mess.”

The Swiss shutdown is the latest example in a string of upheaval at airports and airlines that has disrupted travel across Europe in recent weeks. Staffing shortages lingering from the Covid-19 pandemic have been at the heart of delays and cancellations at hubs in the UK and the Netherlands, with strikes in France and spate of IT outages adding to the chaos. 

Despite its small size, Switzerland’s airspace is crucial for European flights due to the country’s location at the heart of Europe. Zurich Airport, Switzerland’s largest, handles more than 300 departures a day, while Geneva has around 220, according to data from FlightRadar24. During the shutdown, arriving long-haul flights were diverted to Lyon, Milan and Vienna. 

Airlines have lobbied for years to unify Europe’s fragmented air traffic control system. The effort, dubbed Single European Sky, would improve efficiency and offer more direct flight paths, proponents of the system say.

There’s no indication at this point the shutdown was related to malicious cyberactivity. Still, the Swiss National Cybersecurity Centre is in contact with Skyguide about the disruption, a spokeswoman said.

Switzerland has seen a surge in malicious actions from hackers in the past year. The number of cyberattacks reported to the NCSC has reached 800 in recent weeks, compared with 300 a year earlier, data shows.