KADENA AIR BASE, Okinawa — Twenty commercial planes were diverted from Naha International Airport after a computer malfunction forced Kadena Air Base traffic controllers to shut down their radar system Tuesday morning.
A computer system that overlays maps over radar screens malfunctioned, according to an Air Force news release.
The Kadena Airport Surveillance Radar, which controls all airspace within a 50-nautical mile radius of the base, was shut down from 8:49 a.m. to 12:20 p.m.
Inbound and outbound flights at Naha International Airport were affected, said Tetsukazu Taki, a spokesman for the Naha Airport Office of the Land, Infrastructure and Transport Ministry.
“Some of them diverted their destinations to Shimoji, Miyako or Kagoshima,” Taki said.
Some flights were delayed up to 70 minutes, Taki said, while others returned to their take-off points.
Air Force maintenance teams realigned the system, which as of late Tuesday was working normally, the news release stated.
Air traffic controllers relied on backup procedures to land aircraft that were not diverted Tuesday morning, according to an Air Force spokesman.
When radar is unavailable, pilots report their position and altitude to traffic controllers at fixed intervals while maintaining continuous contact. Pilots use ground-based navigation aids to mark their positions.
This method makes traffic congestion a concern. Without radar, planes must keep about 81 miles of separation, according to the Japanese ministry. Air traffic controllers keep planes four to six miles apart when the radar system is working.
U.S. and Japanese authorities have agreed to procedures for nonradar traffic control, the Air Force spokesman said.
Kadena Air Base officials are in the midst of training Japanese personnel for the Japanese government’s eventual takeover of the airspace. The handover is expected to take place sometime in 2007, the spokesman said.
Chiyomi Sumida contributed to this report.