Air travellers in Germany could face chaos this week after air traffic controllers at Frankfurt airport said Wednesday they would stage temporary walkouts in a bitter dispute over pay. GdF, the German union for air traffic controllers, said 200 so-called \"apron control\" staff -- those in charge of directing aircraft in and out of their parking positions -- would halt work between 3:00 pm and 10:00 pm (1400-2100 GMT) on Thursday. The strike could effectively paralyse Germany\'s largest airport and Europe\'s third-largest hub. GdF made its announcement after Fraport, the company which owns and operates the airport, turned down mediation proposals in their wage dispute. The union argues that apron controllers\' pay does not take into account the additional complexity resulting from the opening late last year of a fourth runway in Frankfurt. Fraport denounced the action as \"irresponsible\" and \"incomprehensible\", but pledged to limit disruption as much as possible. \"If someone refuses to budge an inch on double-digit demands that include increases of between 50-70 percent in wages, working hours and bonuses, they\'re acting irresponsibly,\" said Fraport board member and industrial relations director Herbert Mai. Fraport said it had already drawn up contingency measures \"to keep operations up and running as far as possible. But delays and cancellations cannot be ruled out\". Mai said the company was ready to return to the negotiating table \"in so far as GdF is prepared to talk sensibly\". The union repeatedly threatened strike action last year in a long-running wage dispute for regular air traffic controllers. A strike was finally averted when both sides finally reached a deal in October. Investors appeared unfazed by the prospect of the walkout, with Fraport shares gaining 0.45 percent to 45.01 euros and Lufthansa rising 1.9 percent to 10.7 euros on the Frankfurt stock exchange.