Lufthansa IT outage grounds flights worldwide.

After an IT issue at Germany’s flag carrier Lufthansa caused aircraft delays and disruption at airlines across the company, thousands of customers were left stranded globally.

An IT system problem that affects the entire group, a spokeswoman told reporters.

The company said that damage to multiple glass-fiber cables owned by Deutsche Telekom during construction in Frankfurt was the root of the issue. The afternoon on Wednesday would be needed for repairs, according to Lufthansa.

Thousands of travelers were waiting to be checked in when photos and videos from multiple German airports showed turmoil.

At 1017 GMT, Lufthansa’s stock price was down 1.5%. Lufthansa also owns SWISS, Austrian Airlines, Brussels Airlines, and Eurowings.

On social media, travelers said that the company’s breakdown had forced it to organize airline boarding with pen and paper and that it was unable to digitally handle customers’ luggage.

Lufthansa stated this in a tweet: “An IT disruption is currently affecting the Lufthansa Group’s airlines. Flight cancellations and delays are a result of this. We are sorry for the trouble this is giving our customers.”

Bloomberg News reported that Lufthansa had canceled every flight, but the airline informed reporters it was unable to confirm that.

A corporate representative stated, “There are still flights in the air, and they will not be brought to the ground.”

Federal cybersecurity organization BSI of Germany was not immediately available for comment.

The IT failure occurred two days before the planned strikes at seven German airports, which are anticipated to cause significant disruptions, including possibly at the Munich Security Conference where world leaders are anticipated to convene.

The Scandinavian airline SAS reported Tuesday night that it had been the target of a cyberattack and advised customers not to use its app, but later stated that the issue had been resolved.

In what was believed to be the second instance of sabotage against Deutsche Bahn in as many months, unidentified attackers severed cables belonging to Germany’s public train in December.

Following the failure of a crucial federal computer system last month, airlines in the United States canceled more than 1,300 flights and caused over 10,000 delays.