A disk failure in a Sun Microsystems server caused the US Federal Aviation Administration's NOTAM database to crash for nearly 20 hours last week, according to the FAA.

The NOTAM (notice to airmen) system provides notices to airmen, or pilots, regarding airports, equipment, and security issues. The system went down late May 22 and was back up at around 7 p.m. May 23.

Because of the disk failure, information had to be delivered to pilots through local air traffic controllers and alternate systems, including a Web site set up to disseminate the most up-to-date information, said Barry Davis, manager of Aeronautical Information Management for the FAA. However, flight safety was never a problem, the FAA said.

"What happened was the drive in an end-of-life Sun box failed in the middle of updating the information on the hard drive, so it screwed up the database," Davis said.

Davis said that was the beginning of the complications. Davis' team replaced the hardware and the drive on May 22 which got the system running again.

"We already had the equipment to replace [the box], we just hadn't done it yet, and that's why the hardware recovery was quite simple - we just put the boxes in," Davis said.

But even then, the system was running slowly, or in a deteriorated mode, and it got so bad, Davis said, that his team decided to reopen the problem to see what was going on.

As the technicians were working to fix the database, they decided to go to the back-up system. As they did do, they soon realized they had written the error over to the back-up system and had corrupted that system as well, Davis said.

"So because we had already replaced the hardware and the drives, we just had to pull the latest information and extract it out of the [corrupted] database, then re-import it into the [new] database," Davis said. "Then we resynchronized all of the subsystems so everyone had the same database copy, and then we opened the gates up at 4:40 p.m. on Friday so that all of the information would come into the system."

Davis and his team spent the rest of that night monitoring the situation to make sure there were no other errors.

While the automated system was out, pilots and other affected organizations were able to get the latest information from a Web site set up for that purpose. Although everything was updated by 7 p.m. Friday, Davis said the decision was made to keep the Web site up until midnight as a precaution.