German carrier says it expects its flight operations to stabilise by Wednesday evening.

The carrier said repair work would continue until Wednesday afternoon, citing information it had received from Deutsche Telekom, a German telecoms operator. It expects flight operations to stabilise by early evening.

Shares of Lufthansa, which also owns SWISS, Austrian Airlines, Brussels Airlines and Eurowings, were down 1.25 percent at 11:44 GMT.

The local news portal Hessenschau said there had been telecom disruptions affecting the greater Frankfurt area.

Frankfurt Airport, the main centre of Lufthansa’s operations, has been diverting all incoming flights due to capacity concerns.

Lufthansa has also cancelled or delayed domestic and international flights at other airports.

Photos and videos from several German airports showed thousands of passengers waiting to be checked in.

Passengers said on social media the failure had forced the company to organise the boarding of planes with pen and paper and that it was unable to digitally process passengers’ luggage.

Bloomberg News said Lufthansa had grounded all of its flights, but the company told Reuters news agency it could not confirm that.

“There are still flights in the air, they will not be brought to the ground,” a spokesperson for the company said.

Data from aviation website Flightradar24 showed Lufthansa had 40 flights in the air at 10:23 GMT, compared with 105 flights of rival national airline Air France and 121 of British Airways.

The IT system failure comes two days before planned strikes at seven German airports that are expected to lead to serious disruptions, including potentially at the Munich Security Conference where world leaders are expected to gather.

Scandinavian airline SAS said it was hit by a cyberattack on Tuesday evening and urged customers to refrain from using its app, but later said it had fixed the problem.

Unknown attackers cut cables belonging to Germany’s public railway in December in what was seen as a second act of sabotage against Deutsche Bahn in as many months.

Airlines cancelled more than 1,300 flights and more than 10,000 were delayed in the United States last month after the breakdown of a key government computer system.