FILE PHOTO: Lufthansa airplanes are seen parked on the tarmac during a strike of cabin crew union (UFO) at Frankfurt airport, Germany November 7, 2019. REUTERS/Ralph Orlowski

FRANKFURT/BERLIN (Reuters) - A trade union representing Lufthansa’s cabin-crew on Wednesday threatened strikes that could fall during the busy Christmas period if Germany’s biggest airline does not make concessions in a wage dispute.

Trade union UFO said that if no progress was made during talks, it would announce next Thursday when and where strikes would take place and for how long they would last.

A Lufthansa spokesman said the airline would use the time to try to come to an agreement with UFO, adding that a solution could only be found in joint discussions and arbitration.

“You can’t strike and arbitrate at the same time,” the spokesman said.

Cabin crew held a strike over pay and pensions for two days earlier this month, resulting in the cancellation of one in five flights, affecting around 180,000 passengers and costing the airline 10-20 million euros ($11-$22 million).

Last week, Lufthansa and UFO agreed to enter large-scale arbitration talks over pay and pensions, averting further strikes.