Frankfurt, Feb 15 (IANS): An IT breakdown at Lufthansa on Wednesday caused flight delays and cancellations at major German airports, upending the travel plans of thousands of passengers.

Since Wednesday morning, planes and passengers have been jammed in Frankfurt and Munich airports because the computer systems for check-in and boarding, among other things, were no longer operational, Xinhua news agency reported.

"During construction work in Frankfurt, fiber optic cables belonging to a telecom service provider were damaged, causing an outage of Lufthansa's IT systems at Frankfurt Airport," Lufthansa tweeted.

"Flight operations are expected to stabilize in the early evening," it added.

Due to the serious IT glitch at Lufthansa, German air traffic control is no longer routing aircraft to Frankfurt Airport to prevent the hub from filling up, said an air traffic control spokesman. The planes will be diverted to other airports such as Nuremberg, Cologne or Dusseldorf.

A crisis team met at Lufthansa headquarters and is working intensively to find a solution, a Lufthansa spokeswoman said.