The walkouts by ground crew who guide aircraft to parking positions began last week and were due to continue until the weekend.

Airport operator Fraport (FRAG.DE) earlier on Wednesday wrote to the GdF union, proposing new talks without preconditions, but only if the strike was called off.

The GdF, which wants higher pay and shorter working hours, said it would end the strike at 2100 GMT and hoped to start new talks with Fraport on Thursday.

Just over a thousand flights have been cancelled since last Thursday, the vast majority of them from flagship carrier Lufthansa (LHAG.DE), which has mostly scrapped European services to give priority to intercontinental travellers.

Lufthansa (LHAG.DE) accounts for more than half of flights at the airport. It said the first four days of the strike have so far cost it a high double-digit million euro sum in turnover.

Analysts previously estimated the first two strike days had crimped turnover by about 40 million euros. Lufthansa had group revenue of 27 billion euros in 2010.

Lufthansa's shares have barely been affected so far but on Wednesday were down 3.3 percent. Fraport said it has lost turnover of around 7 million euros.

It expected around 174 cancellations from a total of 1,260 slights scheduled on Wednesday. The Lufthansa website showed just over 140 cancelled flights on Wednesday.

More flights may have to be cancelled on Thursday as planes are out of position, Fraport said.

BITTER DISPUTES

Fraport Chief Executive Stefan Schulte said Fraport had the support of Lufthansa, other airlines and airports, and did not want to resort to legal measures to avoid aggravating the situation.

The GdF was also involved in a bitter dispute over pay for air traffic controllers last year that went to the courts and ended with the transport ministry stepping in to force talks.

Fraport has been using former ground crew to replace striking workers, with the number of flight cancellations dropping each day as staff became used to the role again.

Fraport had said it will not agree to what it says are "unreasonable" demands for pay rises of 50-70 percent for a group making up only around 1 percent of its total workforce.

The union has said the workers' jobs have become more complicated since a fourth runway came into operation.

An attempt at mediation in early February failed, with Fraport rejecting the mediator's proposals, saying they went beyond what the union had been demanding.

Frankfurt is Europe's third largest airport behind London Heathrow and Paris Charles de Gaulle in terms of passenger numbers.

(Additional reporting by Peter Maushagen and Maria Sheahan; Editing by Mark Potter)

• A Permanent Economic Emergency