BERLIN -- A German labor union is calling on security staff at Frankfurt airport to go on strike next week in a dispute over pay.
The union said it couldn't rule out other airports being affected by walkouts.
Ver.di said it is still waiting for employers to put forward a negotiable offer for around 23,000 security staff.
Earlier strikes resulted in the cancellation of hundreds of flights at Duesseldorf, Cologne-Bonn, Stuttgart and Berlin's two airports in recent days.
The union wants hourly pay for all workers conducting security checks to rise to 20 euros ($23.10). Employers association BDLS says this could amount to a 30-percent increase in some cases.
Frankfurt is the main hub for Germany's biggest airline, Lufthansa. The company said Friday that it will publish planned cancelations on its website on Sunday afternoon and that it expects a "significant" impact on flights.
Lufthansa said that passengers with a flight from Frankfurt can rebook for free onto another flight between Jan. 11 and Jan. 20.