A software problem at DFS Air Traffic Control Center in Langen forced air traffic controllers to reduce traffic over many parts of Germany for days.
Lufthansa already cancelled 46 flights (Monday). At least 4,500 passengers have been affected by the cancellations.
The software malfunction is affecting the German airports of Frankfurt am Main, Cologne/Bonn, Stuttgart and Dusseldorf.
The software concerned provides the pilots with all data relevant to the flight history of each flight with type of aircraft, route and expected fly-by time.