The GdF air traffic controllers' union said around 200 airport staff members would go on strike at Frankfurt Airport from 3 p.m. to 10 p.m. on Thursday.

"We presume that we will create massive difficulties for Fraport," said union chief Markus Siebers in Berlin on Wednesday.

Negotiations between the union and Fraport, the company that owns and operates the airport, over pay increases had broken down after Fraport rejected a mediator's recommendations to resolve the dispute.

The GdF is acting on behalf of over 200 people who work as air traffic controllers and directing planes into and out of parking spaces on the runway.

Fraport board member Herbert Mai said the strike threat was unacceptable, adding that the company had fulfilled nearly all of employees' demands.

He said Fraport would try to keep the airport operating "as far as possible" but that delays and cancelled flights could not be ruled out.

GdF chief Siebers estimated that around 400 flights would be affected by the strike, around 30-40 percent of the 1,250 flights daily.

ncy/rc (dpa, dapd, AFP)