Cabin crew staff members of the German airline Lufthansa have warned that they plan to stage more strikes over their wage and working conditions.
The crew union, UFO, said on Saturday that the staff can go on strike "every four days, or fortnight or every three weeks" if mediation talks are abandoned.
The warning came one day after Lufthansa and union representatives agreed to begin a formal mediation procedure. Recent strikes forced Lufthansa to cancel hundreds of flights.
The UFO union has demanded a five-percent pay increase and guarantees that jobs will not be outsourced to temporary workers.
However, Lufthansa has only offered a pay increase of 3.5 percent in exchange for longer hours.
In 2009, a similar strike by cabin crews cost Lufthansa tens of millions of euros.
The airline normally operates about 1,800 flights a day around the world.