German flag-carrier Lufthansa said it would cancel two thirds of Friday's flights after a cabin crew union announced a 24-hour stoppage at six major airports.
The Independent Flight Attendants' Organisation (UFO) announced the strike late on Wednesday, one day after its members staged eight-hour walkouts at three key German airports as part of a dispute over pay and conditions.
The strike Friday would hit Frankfurt, Berlin, Hamburg, Munich, Duesseldorf and Stuttgart, said a statement on the union's website.
The latest call for action marks an escalation of an ongoing industrial dispute, as Tuesday's action targeted only Berlin, Frankfurt and Munich airports and lasted only eight hours.
That strike forced Lufthansa to cancel over 200 flights at its Frankfurt hub, Europe's third busiest.
UFO represents some two-thirds of Lufthansa's 18 000 cabin crew.
It is seeking a five percent pay increase backdated to January after three years of wage freezes. It is also opposed to the use of temporary cabin crew on Lufthansa aircraft.
Lufthansa spokesman Klaus Walther earlier said the airline had offered a salary raise of about 3.5 percent as well as an offer to stop fixed-term contracts and halt the use of temporary staff.
The airline already faces headwinds because of rising fuel prices and fierce competition.
A 2009 strike by cabin crew cost Lufthansa tens of millions of euros.
In February this year, Frankfurt airport's apron control staff - traffic controllers who guide aircraft on the tarmac -walked off the job over demands for higher pay.