A mysterious server problem at Incheon International Airport paralyzed air traffic control for almost an hour on Wednesday, wreaking havoc with flight schedules. Planes heading to Korea from China and Japan or scheduled to fly over Korean air space were also forced to delay their takeoff.

"An error occurred at the server that powers the Air Traffic Center, but we still haven't been able to find the cause of the problem," said an official with the Ministry of Land, Transport and Maritime Affairs, which oversees the ATC.

Traffic control at Incheon International Airport handles an average of 1,400 aircraft that land or take off from Korean airports or pass Korean airspace.

When the main computer server at Incheon failed at around 10:30 a.m. on Wednesday, the ministry told air traffic controllers at Incheon, Gimpo and Jeju to have aircraft take off at four-minute intervals as opposed to the usual one- or two-minute intervals. When efforts to fix the error dragged on, the ministry increased the interval to 10 minutes.

At around 10:45 the ministry informed the Japanese and Chinese governments of the problem and asked air traffic controllers there to delay takeoff by 10 minutes for flights headed to Korea or scheduled to pass through Korean air space.

The error in the server was fixed at around 11:30 a.m. and air traffic control went back to normal. But already some 20 flights scheduled to depart from Incheon, Gimpo and Jeju had been delayed by more than 30 minutes.

Because there is only one air traffic control center in Korea, there have been concerns that an emergency could lead to serious problems in flight control.