Deutsche Lufthansa AG canceled more than a third of its flights on Tuesday due to a strike by security staff at eight German airports, including the airline’s main hubs in Frankfurt and Munich.

About 500 of the 1,300 scheduled services were scrapped, the airline said. Security workers at the airports, which also include Hamburg, Hanover, Bremen, Dresden, Leipzig/Halle and Erfurt, have staged a walkout as the Ver.di union pushes for higher wages.

At Frankfurt airport, Germany’s largest, about 600 flights or half of the total scheduled for all airlines were called off, a spokesman for operator Fraport AG said.

Talks between Ver.di and the employers’ group representing security operators will start again on Jan. 23.