Berlin: Frankfurt Airport said it will cancel or divert all incoming flights to the airport after an IT system failure at Lufthansa forced the airline to cancel dozens of flights on Wednesday.
German air traffic controllers said Lufthansa aircrafts could no longer depart from Frankfurt Airport and were parked there, meaning no parking positions were available for other aircraft.
"There is a group-wide IT system failure," a spokesperson told Reuters.
The airline said it is working intensively to solve the problem.
The company said the problem was caused by damage to several of Deutsche Telekom's glass-fibre cables during construction work in Frankfurt. Repairs would take until Wednesday afternoon, Lufthansa said.
Photos and videos from several airports across Germany showed chaos with thousands of stranded passengers waiting to be checked in.
In a tweet, Lufthansa said: "Currently, the airlines of the Lufthansa Group are affected by an IT outage. This is causing flight delays and cancellations. We regret the inconvenience this is causing our passengers."
Shares in Lufthansa, which also owns SWISS, Austrian Airlines, Brussels Airlines and Eurowings, were down 1.5 per cent at 1017 GMT.
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.