Honolulu International Airport suffered a radar failure Thursday morning at a time when more than 40 planes were in the air, but backup procedures worked smoothly and the situation never became dangerous, a federal official said yesterday.

Ian Gregor, Federal Aviation Administration spokesman for the Western Pacific, said radar scopes at the airport went black for nine minutes at about noon on Thursday. There were 47 planes in the air at the time, Gregor said.

"The good news," Gregor said, "is that we have procedures in place to deal with these situations and our air traffic controllers, supervisors and managers are all well-trained in these procedures. They immediately responded and handled the situation by going to Plan B.

"Everybody performed brilliantly."

He said the situation affected all air space in the Hawaiian Islands.

"It had no real impact on the traveling public but it was a big deal to everyone working at the time," Gregor said.

During the backup procedures, he said, air traffic controllers communicate with planes in the air by radio, monitor their flight paths and keep them at different altitudes so there is no threat of collision. Any planes on the ground awaiting takeoff are held up until the problem is fixed.

Gregor said any flight delays that resulted were less than 15 minutes.

He said the cause of the problem was a maintenance error on the radar system, either because a worker made an error or because the instructions being followed were faulty.

"We are implementing steps to ensure that there is no reoccurrence," Gregor said. "Nothing like this has happened at the Honolulu Airport before."