Washington — If there was good news from the air-traffic computer system failure that forced thousands of flights in the eastern United States to be scrubbed or delayed Saturday, it's that it never threatened to become a catastrophe.

"There was a lot of inconvenience and a loss of service, but there was never a loss of safety," John Hansman, a aeronautics professor at the Massachusetts Institute of Technology, said in an interview. "The good news is they were able to go to backups."

Flight disruptions persisted within the U.S. Sunday as airlines attempted to recover from the hours-long failure at a Federal Aviation Administration facility in Leesburg, Virginia, near Washington. The center oversees long-range flights in airspace between New York and Atlanta. The breakdown caused 492 delays and 476 cancellations, according to an FAA statement.

Impacts on travelers were greater as the disruptions reverberated through the interconnected aviation-route network. The tracking website Flightaware.com counted more than 6,000 delays and 700 cancellations in the U.S. during the weekend, though some were for other reasons.

The FAA is focused on a recent software upgrade as the trigger for the shutdown, the agency said in an emailed statement on Sunday. The software was returned to an earlier version and the system appears to be functioning fine, the agency said. The agency hasn't seen additional failures, and air-traffic flowed normally Sunday, it added.

The failure occurred in a new system called En Route Automation Modernization, or ERAM, that's installed at 20 FAA centers that guide mostly high-altitude traffic. The final center to get ERAM was in New York, where it became operational in March, according to an FAA press release.

"There is no indication that the problem is related to any inherent problems with the En Route Automation Modernization system, which has had a greater than 99.99 availability rate since it was completed nationwide earlier this year," the FAA said in its statement.

Built by Lockheed Martin, ERAM was designed to provide a foundation for much of the new technology being installed in coming decades that will supersede air traffic control systems based on radar. It replaced software that was as much as 40 years old, according to the Transportation Department's Inspector General.

ERAM has helped the FAA to introduce text messaging to the cockpit that partially replaces the radio calls between controllers and pilots. It also displays the position of aircraft using satellite-based tracking technology. Controllers using it can give pilots more efficient routes into and out of airports.

ERAM is more functional than the system it replaced, and air-traffic controllers have been happy with its improvements, Hansman said. And while the air-traffic system may still be vulnerable to technology failures, it's been designed with multiple backups and cautionary procedures that allow controllers to ensure safety, Hansman said.

David Grizzle, a consultant who formerly was the FAA's air- traffic chief, said ERAM has far greater capacity than the old system. "And even before we completed its installation, it had far higher reliability," Grizzle said in an interview.

It's too early to jump to conclusions about what may have triggered Saturday's failure or whether it represents a flaw in ERAM, Grizzle added.

In its early years, the system was plagued by software glitches and cost overruns, according to inspector general reports. The agency expected to pay an additional $330 million above the $2.1 billion budget for ERAM, according to a 2013 report.

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