Private security workers at two German airports, Duesseldorf and Cologne-Bonn, walked off the job Thursday in a one-day warning strike.
The strike, part of an ongoing dispute over wages, caused dozens of flight cancelations.
At Cologne-Bonn airport, 40 of 190 flights were canceled, and at Duesseldorf, 205 of 530 were canceled, according to German news agency Deutsche Presse-Agentur.
The workers are represented by the ver.di union, which called the strike to put pressure on employers ahead of the next round of negotiations.
Three rounds of talks have failed, and the next round is set to begin Feb. 5.
The union is asking for pay raises of 1.5 euros ($1.70) to 2.5 euros ($2.83) per hour.
Travelers should check with their airline regarding the current status of their flight.
Additional reporting by The Associated Press