German air traffic controllers are to strike for six hours on Thursday in support of pay demands, their trade union Tuesday.The strike could affect up to 2,500 flights from 06H00 to 12H00 (0400 TO 1000 GMT) on Thursday, at the height of the holiday season.Out of a total of 5,500 air controllers, 3,400 belong to the GdF union which has called for all employees to take part in the strike.Deutsche Flugsicherung (DFS), the company responsible for air traffic, said it would likely ask on Wednesday for a temporary court injunction against the strike, said Jens Bergmann, head of personnel.Over 95 percent of union members earlier voted for all-out strike action, union president Michael Schaefer said Monday.The union is demanding a 6.5-percent pay increase for its members, along with better working conditions, but management has offered just 4.1 percent over two years, according to a union statement.Some controllers will be on duty to ensure essential flights can take place, the union added.