The airport's operator Fraport (FRAG.DE) has rejected a mediator's proposal in negotiations over wages for 200 so-called apron control staff, who work around aircraft parking positions, the union of German air traffic control workers GdF said on Thursday.

The union will decide by the middle of next week over a possible strike, which could take place Thursday, February 16, at the earliest, it said.

Apron controllers' pay no longer reflected the additional complexity resulting from the recent opening of a fourth runway at the Frankfurt airport, the union added.

Fraport's head of personnel, Herbert Mai, described the strike threat as "absolutely out of proportion".

Air traffic controllers' union GdF kept German air passengers on tenterhooks for months last year, when it was trying to push wage demands for regular air traffic controllers, repeatedly threatening to strike.

The employer, Germany's DFS air safety authority, fought the union in court and both sides finally reached a deal in October, averting a strike that would have disrupted thousands of flights across Europe.

(Reporting by Peter Maushagen and Ludwig Burger)

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