Hamburg - The main doors of Hamburg's airport were sealed to arriving passengers on Monday after security personnel went on strike in a dispute over pay.
Police shut the doors after normal security clearance procedures collapsed during the one-day strike, which also affected the airports in Stuttgart and Hanover.
"The latest situation is catastrophic," Hamburg airport spokesperson Stephanie Harder said. "We have surpassed our capacity limits."
A quarter of flights there were cancelled, she said, and passengers have been asked to postpone their travel.
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Passengers had been warned to expect lengthy delays and cancellations ahead of the strikes at the three airports, which handle on average 80 000 passengers a day.
The union Verdi is looking for an increase in hourly wages for security workers of 70 cents to €2.50.
The three airports are among Germany's busiest. Striking personnel include those who work with the public as well as those who guard company buildings at airports and military and nuclear facilities.
A spokesperson for the employers, Ralph Beisel of the German Airports Association, called the strike a great imposition on passengers and demanded the union get back to the negotiating table.
Workers at the largest of the three airports, Hamburg, already started walking out during the night. About 40 000 passengers could be affected there.
The authorities in Stuttgart said passengers could expect delays of an hour and advised people to get to the airport three hours before they were due to fly.
Verdi's spokesperson in Hanover, Ute Gottschaar, called on the employers to get back to the negotiating table.
An airport spokesperson in that northern city, Soenke Jacobsen, said few adverse affects were seen on its travellers. "Currently, we have no cancellations, and delays are marginal," she said.
The next round of talks are due to take place Wednesday in Hamburg.
"We hope the strike will be enough to ensure a deal at the talks on Wednesday," Verdi spokesperson in Hamburg Peter Bremme said.