US flights grounded after system outage

Thousands of flights across the United States were temporarily grounded for hours on Wednesday by the Federal Aviation Administration (FAA) after its computer system experienced an outage that was later fixed, allowing flights to resume "gradually".

The FAA grounded all domestic flights from 7:20 am Eastern time across the country after its system failed at 8:28 pm on Tuesday. It was the first time the FAA had taken such action since the terror attacks of Sept 11, 2001.

It lifted the ground order by 9 am Wednesday after it fixed the "Notice to Air Missions", or NOTAM system, which sends key safety alerts to pilots about conditions that could affect their flights.

Pilots must consult NOTAM before takeoff for safety information on towers, lights on runways, or events taking place near an airport. The system is different than the air traffic control system that ensures planes maintain a safe distance from each other.

The FAA said in a statement on Twitter: "Normal air traffic operations are resuming gradually across the US following an overnight outage to the Notice to Air Missions system that provides safety info to flight crews. The ground stop has been lifted. We continue to look into the cause of the initial problem."

But even as normal air traffic operations resumed nationwide, more than 8,600 flights were delayed by the early afternoon, and more than 1,250 flights were canceled, data from FlightAware, a website that tracks delays and cancellations showed.

Airports in New York, Chicago, Los Angeles and Atlanta saw between 30 and 40 percent of flights delayed.

Internationally, flights to the US still took off from Amsterdam's Schiphol Airport, Paris' Charles de Gaulle airport and London's Heathrow Airport. None of the international airlines reported cancellations, but they were severely delayed.

Shabnam Amini, a resident of Dallas, Texas, boarded Americans Airlines Flight 51 at 10 am at Heathrow Airport. But she and other passengers had to sit on board for almost three hours because of delays from the FAA outage.

A backup NOTAM system started on Tuesday night, but the data was corrupted and unreliable. The system was rebooted the next morning, but it took time to work.

The FAA problem came just weeks after Southwest Airlines was forced to cancel tens of thousands of flights after Christmas, when its own system failed, creating travel chaos for passengers.

The airline is allowing passengers to change flights due to the FAA computer outage. At least 377 flights were canceled.

Southwest said in a statement: "As a result of the FAA's outage, we anticipate some schedule adjustments will be made throughout the day."

United Airlines also warned passengers of ongoing delays. "United has activated a travel waiver for any customers who need to change their plans, including offering refunds for customers who no longer want to travel," it said in a statement.

US President Joe Biden said he had been briefed by Transportation Secretary Pete Buttigieg. A thorough "after-action" investigation is underway.

White House Press Secretary Karine Jean-Pierre said that there was "no evidence of a cyberattack at this point".

Canada also announced that its NOTAM system went down on Wednesday morning but was later fixed.

Buttigieg told CNN that the FAA had simply acted "to make sure that passengers are safe". He added that "we have to understand how this could have happened in the first place" and said an investigation would uncover if the FAA's system was outdated.

Geoff Freeman, president and CEO of the US Travel Association, wrote on Twitter: "Today's FAA catastrophic system failure is a clear sign that America's transportation network desperately needs significant upgrades.

"Americans deserve an end-to-end travel experience that is seamless and secure. And our nation's economy depends on a best-in-class air travel system."

Democratic Senator Maria Cantwell, chair of the Senate Committee on Commerce, Science and Transportation, said that they plan to investigate the causes behind the outage.

The FAA has had no permanent executive since March because Biden's nominee Phillip Washington, the current CEO of Denver International Airport, has not been through a confirmation hearing.

Agencies contributed to this story.