Sixty-six flights to and from Germany's busiest airport Frankfurt were canceled on Monday amid ongoing technical problems affecting air traffic control.
Around 4,500 passengers traveling with the German airline Lufthansa were affected when 46 of its flights were scrapped.
A "software malfunction" has caused problems at the state-owned air navigation service provider DFS since last Wednesday, the company said, but assured the public that "the safety of air traffic is not impaired."
Until new software is installed on Thursday, air traffic has been reduced to 75 percent capacity for safety reasons, impacting flights using Frankfurt, Cologne-Bonn, Stuttgart and Düsseldorf airports.
Software update to blame
The problem affected the system that transmits flight data such as aircraft type, route and expected time in the relevant airspace to air traffic controllers.
DFS said the glitch affected the Langen control center after a software update in February.
"Technicians are working intensively to analyze the fault," the company said.
ta/rt (AFP, dpa, Reuters)