"It appears to be an internal software processing error, but we're going to have to do some forensics on it," said Hank Krakowski, chief operating officer of the FAA's Air Traffic Organization. "These are very complicated systems."
The error occurred around 1 p.m. Eastern time, shutting down a central computer system in Atlanta, Ga. NADIN operates on a load-bearing system, so when the main facility went down, requests for flight plans shifted to a backup system in Salt Lake City, Utah. But that system was overwhelmed by the volume and began rejecting requests for flight plans, making it impossible for hundreds of planes to get off the ground.
Radar systems were unaffected, and air traffic controllers gave priority to planes that were running low on fuel, enabling flights already in the air to land safely.
The delays were worst in Atlanta, which also was affected by a severe storm. Chicago's Midway Airport, Boston's Logan Airport, Baltimore's Thurgood Marshall International Airport and Dallas's Love Field also experienced substantial delays, though Krakowski said the situation was improving as of 5:15 p.m. Eastern.
Krakowski said the agency did not believe that the error was caused by computer hackers.
The FAA experienced a similar problem in June 2007, when an error in NADIN in Atlanta caused a system crash, and the resulting workload overwhelmed the Salt Lake City backup. But Diane Spitaliere, a FAA spokeswoman, said that she had been told that the Tuesday software error was different from the 2007 flaw.
NADIN was built and is maintained by Hughes Network Systems. In June of this year, FAA awarded a maintenance contract to Hughes worth up to $900,000 over five years, with a minimum price of $5,000 per service call.
Ken Donoghue, a spokesman for Stratus Technologies, the company that manages the hardware behind NADIN, said that as of 5 p.m. Eastern, there was no indication of a hardware failure. The company would know, he added, because the system automatically sends an alert in the event of a failure, noting which component of the system is involved.
"The air traffic control system, everyone admits, is antiquated," said Roger Dow, the president and chief executive officer of the Travel Industry Association. "We need a true world class system."
Coincidentally, Dow was in Denver for the Democratic National Convention, pushing the presidential candidates to address air travel delays that have irked passengers over the past several months. He said that the system failure was putting a crimp in his plans. "We're already getting calls from people who aren't making it to the convention."