Security workers at most of Germany’s major airports walked out on Thursday in a one-day strike to step up pressure in a pay dispute, prompting widespread flight cancellations.

The ver.di union, which announced the walkout on Tuesday, called on workers to strike at Frankfurt, Berlin, Cologne, Duesseldorf, Hamburg, Stuttgart, Leipzig, Hannover, Dresden, Bremen and Erfurt airports.

Airports in Bavaria ,including Munich, the country’s second-busiest, were not affected.

All departures for the day from Berlin, Hamburg and Stuttgart were cancelled before the strike started. About four-fifths of flights in Cologne and one-third in Duesseldorf were cancelled.

In Frankfurt, the operator of Germany’s busiest airport said security checkpoints outside the transit area would remain closed.

It advised passengers planning to start their journeys there not to go to the airport. However, there were connections for transferring passengers; Lufthansa planned to operate much of its planned schedule, including intercontinental flights.

Airport operator group ADV estimated that about 1,100 flights would be cancelled or delayed, affecting some 200,000 passengers, German news agency dpa reported.

Three rounds of talks have failed to produce a pay agreement for some 25,000 security workers.

In a separate dispute, ver.di has called for strikes on Friday on local public transportation systems in much of the country.

A bitter dispute over working hours and pay resulted in full-scale strikes last month that affected Germany’s passenger trains.

The GDL union, which represents many of the country’s train drivers, on Monday ended a five-day strike earlier than originally planned after agreeing to resume talks with the state-owned main railway operator, Deutsche Bahn.