German airports were bracing for widespread disruption and hundreds of flight cancellations from Thursday as ground staff, baggage handlers and maintenance workers threatened to walk out over pay.
Lufthansa, Germany's biggest airline, said Wednesday it will cancel around 600 European and domestic flights until 2:00 pm (1300 GMT) on Thursday in the wake of strikes organised by the giant services sector union Verdi.
"The airlines of the Lufthansa group expect substantial disruptions to air traffic tomorrow, due to the strikes called by Verdi," the airline said in a statement.
"We're expecting around 600 cancellations," a spokesman added.
Lufthansa quoted media estimates that around 6,000 employees in Frankfurt alone would take part in the strike.
But Verdi said it expected around 1,400 people to join the walkouts.
"But there will also be disruptions in Munich, Duesseldorf, Cologne-Bonn, Stuttgart, Hamburg and Hanover," Lufthansa warned.
"In view of the strikes, Lufthansa is cancelling almost all domestic and European connections in Frankfurt and Munich until 2:00 pm (1300 GMT)."
Also affected would be long-haul connections to and from both Frankfurt and Munich, Lufthansa added.
By contrast, flights operated by Lufthansa's Germanwings subsidiary and the regional carriers to and from Munich would not be affected.
At Germany's third-biggest airport in Duesseldorf, a spokesman said delays and cancellations would likely be limited as the pay negotiations concerned just one in 10 employees, an airport spokesman said.
The country's number two carrier, Air Berlin, said it expected to cancel just six flights on Thursday.
"We expect the fallout to be minimal," a spokesman said, but added that the number of flights affected could rise.
In order to limit the anticipated chaos, airlines were advising passengers to check online before travelling to the airport.
And Fraport, which operates Frankfurt airport, said it was advising passengers booked on the cancelled flights not to bother turning up at all.
The national rail operator, Deutsche Bahn, said it will mobilise additional staff on Thursday to cope with the expected increase in rail traffic as air passengers take the train instead.
Under an agreement between the rail operator and the airlines, passengers holding valid tickets for domestic flights on Lufthansa, Germanwings or Air Berlin can swap them for train tickets.
Verdi has been calling for strikes in various public services in recent weeks, ranging from kindergartens to public transport.
But pilots could also stage their own walkouts soon, as well, their union Cockpit warned on Wednesday.