Deutsche Lufthansa AG is returning to normal flight operations after widespread software problems linked to damaged Deutsche Telekom AG broadband cables grounded hundreds of planes.

The situation at Lufthansa’s main base in Frankfurt is normalizing, a spokesman said Wednesday. Lufthansa expects the IT issues that affected systems including check-in operations to be fully resolved by early evening.

Still, more travel disruption is around the corner. Ground staff at Lufthansa’s Frankfurt and Munich hubs are planning strikes on Friday in a move that’s likely to lead to hundreds of additional flight cancellations. The Verdi services union has called the one-day walkout due to slow progress in talks over pay and conditions for security and other staff. The strikes complicate travel for delegates attending the Munich Security Conference, a major annual event for defense and foreign-policy makers.

Wednesday’s disruption, caused by damage to broadband cables at a rail location in northern Frankfurt, forced Europe’s biggest airline by fleet size to ground hundreds of flights worldwide. Lufthansa’s global flight operations center is located on the outskirts of Frankfurt’s airport, so damage to the communications links there ripples through Lufthansa ground IT systems across the world. In Germany, air traffic control had to divert landings in Frankfurt to prevent an overflow.

Deutsche Telekom spokesman Peter Kespohl said that since Tuesday, four broadband fiber cables had been damaged at a Deutsche Bahn Railtrack by drilling work neither commissioned nor conducted by the telecommunications company. Deutsche Telekom has repaired two of the cables and is working on the others, Kespohl said, adding the company couldn’t immediately say how long it will take to finish the repairs.

In total, Lufthansa has around 700 aircraft. Its stable of airlines includes its namesake brand and the national flag carriers Austrian Airlines, Brussels Airlines, and Swiss. The company also operates low-cost carrier Eurowings as well as other smaller brands.

Lufthansa declined 0.44% as of 3:48 pm in Frankfurt. The shares are still up around 24% this year.

The German company is scheduled to report earnings for 2022 next month. In December, the carrier raised its full-year earnings target on rebounding air travel.