BERLIN (AP) — Flight cancellations at Hamburg Airport after a surprise strike by workers affected more than 40,000 passengers on Sunday, a day before a planned wider protest across Germany amid new contract negotiations.

Only 10 of more than 280 scheduled flights went as planned early Sunday, the airport said. Many service desks sat empty as would-be passengers lined up to seek information about the cancellations.

The surprise walkout, which reportedly took place with only about a half-hour advance notice, came before a broader series of preannounced strikes across 13 airports in Germany on Monday, organized by the ver.di union.

The union, whose members work in areas including passenger services and cargo and goods screening, called for Sunday's strike by security control staff to put pressure on company representatives amid collective bargaining talks.

“The behavior of the trade union ver.di is dishonorable: The strike without notice hits Hamburg Airport at the start of the vacation season," airport spokeswoman Katja Bromm said in a statement. She said that on Monday, arrivals would be possible, and that “considerable disruptions and cancellations” were expected.

Bromm said that Sunday's walkouts were "excessive and unfair to tens of thousands of travelers who have nothing to do with the disputes.”

For months, ver.di has been negotiating a new agreement that aims to improve occupational health and safety, provide more vacation days, an increase in the annual bonus to 50% and the freedom to choose a doctor for employees’ regular, mandatory medical exams, among other things.