Passengers were advised on Friday not to bother turning up for flights at Frankfurt airport because of a one-day strike by security staff.
"We have asked passengers not to travel to the airport for now. As things currently stand, the legally required security checks cannot be carried out," said a spokesman for airport operator, Fraport.
The spokesman said that in total 65 flights had officially been cancelled so far, out of a total 1,300 scheduled for the entire day.
Service industry union Verdi called on members employed by private security contractors to stay away from work. A spokeswoman confirmed on Friday that this would be between 2am and 11pm.
Fraport and Germany's biggest airline Lufthansa said they could not estimate the total extent of delays and flight cancellations.
Verdi is fighting for an hourly wage rise to €16, calling an offer by employers of €10 - €13 euros "far too low".