The FAA is looking into what caused the radar display screens at the Honolulu Air Traffic Control Tower to go black for nine minutes yesterday.

The controllers, based in Honolulu, control the airspace for the entire state.

Without the radar display, the controllers are basically blind.

The FAA says this problem had never happened before at the Honolulu facility and it rarely ever happens across the nation.

Around 10:30 yesterday morning, the radar display at the Honolulu Air Control Facility went blank.

"It's one of our worst nightmares. Wake up in a cold sweat, no way that didn't happen," said Scott Sorenson, National Air Traffic Controllers Association.

"This is the first time this kind of problem has ever occurred at the Honolulu facility," said Ian Gregor, FAA Spokesman.

The controllers rely on the radar display to control the air traffic throughout the entire state.

The outage lasted nine minutes.

"You spring into the last mental picture of what the aircraft were doing, and let's say you had 10-11 airplanes doing all different things. You go back to the mental picture where was United, American, Hawaiian, what altitude was he at," said Sorenson.

All ground traffic was stopped, but the controllers brought in the planes using memory and radios.

And sorenson says the veteran controllers took the helm.

"The most junior controller had 18 years of experience ," said Sorenson.

Gregor says there were 47 airplanes in the airspace around the islands at the time -- what he calls "moderate air traffic."

"If this had occurred 10 minutes later we would've had double the traffic volume," said Gregor.

Gregor says fortunately there were no instances where any of the planes got too close to one another.

There weren't even any inbound flight delays.

"The air traffic controllers, supervisors and management in Honolulu did a fantastic job in dealing with this situation," said Gregor.

As for the cause of the outage -- it's still under investigation by the FAA.

"We're investigating whether the problem was caused by an error made by a technician who was working on the system or whether the technician was using flawed procedures," said Gregor.

And Gregor says the FAA has since put procedures in place to prevent this from happening again.

Sorenson says thanks to the teamwork, experience and skill, the controllers helped avert a potentially catastrophic event.