FRANKFURT (Reuters) - German air traffic control agency DFS said on Monday it would try to put a new software version into operation as a system glitch is still causing a 25 percent reduction in air traffic volume in large parts of Germany.

Experts will try to implement the software update on Wednesday night, a DFS spokeswoman said, adding that flight safety is not affected.

The problem has affected DFS’s Langen control centre near Frankfurt where air traffic controllers oversee flights in an area in southwestern Germany comprising several states.

Lufthansa said it had cancelled 46 flights affecting 4,500 passengers, while Fraport said a total of 66 flights had been cancelled.

DFS reduced air traffic volumes in an area stretching from Lake Constance on the Swiss border to the city of Kassel in central Germany and including Frankfurt, Cologne/Bonn, Stuttgart and Duesseldorf airports, last week already due to a software problem in its control centre near Frankfurt.

The software - engineered with a lot of DFS’s own know-how - started having issues displaying planned airplane routes on Wednesday. The software is updated every four weeks with the newest set of data on planes and routes.