NEW YORK (AFP)
Weary travellers endured more flight disruptions as service resumed at US airports after an hours-long total stoppage, with officials saying the situation should return to normal Sunday.
The Trump administration blamed the mess that began Friday on a botched replacement of old copper wire communication lines.
The nationwide ground stop -- meaning no planes can take off -- sparked widespread chaos and left hundreds of thousands of passengers in limbo, with some pulled off planes moments before they were due to depart by airline staff who appeared in the dark about unfolding events.
Federal Aviation Administration (FAA) chief Bryan Bedford said that 12,000 flights were cancelled on Friday and between four and five thousand flights out of 41,000 scheduled for Saturday were likely to be cancelled as well.
As of Saturday evening, the tracking website FlightAware had recorded more than 6,200 cancelled flights.
Speaking at a news conference in Washington, Bedford offered a "sincere apology to the American travelling public."
He predicted a full resumption of flight schedules by "close of business on Sunday."
Transportation Secretary Sean Duffy said Friday's four-hour ground stop was declared after maintenance work to upgrade an old copper wire to a high-speed fibre cable had caused "issues" with communication with airplanes and radar feeds.
"Either through contractor error or a faulty piece of equipment...it started flooding other routers in our air traffic control system," Duffy told reporters.
Friday's disruption was only the second time such a ground stoppage had been issued in US airspace -- which is among the busiest in the world -- since the 9/11 attacks.
The nationwide halt was lifted at 8:15 pm Eastern Time Friday (0115 GMT Saturday).
During the outage, footage from airports showed gates full, with planes waiting on taxiways and passengers thronging concourses.
FAA officials reopened the airspace "after restoring full functionality" at air traffic control facilities, according to Duffy.
Tim Johnson, consumer director at the UK Civil Aviation Authority, said although US flights have resumed, there could be "some follow-on disruption" as airlines re-book passengers and get all services back to normal.
Duffy appealed for $50 billion in funds to upgrade and modernise the air traffic control system, and called for Congress, which controls the purse strings of the US government, to "meet this moment."