A one-day strike by security staff at three German airports on Thursday is causing travel chaos for tens of thousands of travelers, AP reports.

The ver.di union called on staff at airports in Duesseldorf, Cologne-Bonn and Stuttgart to walk off the job all day, leading to hundreds of flights being canceled.

The German news agency dpa reported that 350 flights were canceled at Duesseldorf, 142 at Stuttgart and 131 at Cologne-Bonn.

Up to 110,000 passengers may be affected only by the cancelations at those three airports, according to dpa.

Other airports in the country were also affected by the strike including Berlin where 90 flights had to be canceled at the capital’s Tegel airport and another four at Schoenefeld airport.

“Check the status of your flight at the airline before coming to the airport,” Berlin Airport Service tweeted Thursday morning.

About 100 flights were canceled at Munich’s international airport, though some because of the continuing snowfall in southern Germany.

At Duesseldorf airport, hundreds of security employees protested by blowing whistles and holding banners with slogans like “More salary? For sure!” The departure and arrival displays showed hundreds of cancellations while airlines were struggling to book passengers on other flights or gave out vouchers for train rides instead.

Ver.di has said employers “provoked” the strike by offering a 2-percent pay increase over two years.

The union wants hourly pay for all workers conducting security checks to rise to 20 euros ($23.10). Employer association BDLS says this could amount to a 30-percent increase in some cases. The next round of talks is due on Jan. 23.

Thursday’s action was the second time security employees went on strike this week. On Monday, they staged a walk-out at Berlin’s two airports which caused disruption.