Lufthansa and cabin crew have agreed to mediation in a dispute over retirement benefits after talks failed on Friday, adding to the risk of further costly labor strikes at the German airline. “The position of Lufthansa fell short of what had already been agreed, so further negotiations could not bring any progress,” Nicoley Baublies, the head of cabin crew union UFO, which represents 18,000 workers at Lufthansa, said in a statement on Monday.