German air traffic controllers plan a six-hour strike Tuesday at the height of the holiday travel season to back up demands for pay hikes after calling off planned action last week, their union said.The GdF union said Monday the controllers would stop work at 0400 GMT Tuesday and resume six hours later. Members are demanding a 6.5 percent wage increase. The union withdrew a strike call Wednesday, hours after a court ruling in Frankfurt banned its action in a case brought by the agency responsible for air traffic, the Deutsche Flugsicherung (DFS).The GdF represents more than 3,000 of Germany\'s 5,500 air controllers. The DFS said it would turn to the courts anew to stop Tuesday\'s action, which was not covered by last week\'s court ruling.\"Nothing has changed legally since the last court response to a possible strike,\" a spokeswoman said.\"Unfortunately the controllers rejected our offer for negotiations,\" she added, leading to an \"escalation\" of the conflict.Union representatives refused to sit down with employers after DFS declined to present a new pay offer.Controllers earn between 72,000 and 130,000 euros ($104,000 and 187,000) per year, according to employers.Airlines said they feared major delays Tuesday in the middle of the brisk August travel season.