The union representing ground workers at Frankfurt Airport has said it is extending its strike action until Friday to press its demands for more pay from airport operator Fraport AG.
The strikes, which began last week, have already led to the cancellation of hundreds of flights and delays at the airport, Europe's third busiest, which sees some 1,300 take-offs and landings daily.
Germany's largest airline, Lufthansa, which uses Frankfurt Airport as its main hub, said it only had to cancel an additional 80 round-trip flights - all domestic and European routes - after taking measures to work around the strike by 200 GdF union members.
Fraport says GdF's demands for double-digit wage increases are "absolutely unacceptable", while the union said it just wants the Frankfurt workers' salaries brought in line with what other airports pay.
GdF and Fraport have been unable to come to a new agreement after weeks of negotiations.