Eight German airports, including hubs in Frankfurt and Munich, are bracing for a wave of flight cancellations on Tuesday because of a strike by security staff.

Airport-security workers in Frankfurt, Munich, Hamburg, Hanover, Bremen, Dresden, Leipzig/Halle and Erfurt plan to walk out from 2 a.m. to 8 p.m. on Tuesday as the Ver.di union pushes for higher wages.

“Because employers have shown no willingness to make a better offer, the extension of warning strikes has become necessary,” Ver.di board member Ute Kittel said in a statement on Monday. Talks are due to start again on Jan. 23.

Lufthansa AG, Germany’s largest airline, warned of “significant disruption” at its hub in Frankfurt, with multiple flights due to be canceled. The airline hasn’t yet commented on how the strike will impact flights at other airports.

“These are no longer just warning strikes but completely disproportionate,” Matthias von Randow, managing director of the BDL employers’ group, said Monday. “The wages of security control personnel have increased by almost 50 percent since 2011.”