New York (CNN) — The Federal Aviation Administration on Wednesday lifted an order halting all domestic flights within the United States after reinstating a system that provides pilots with pre-flight safety notifications. The overnight shutdown caused widespread disruption, with thousands of flights still delayed across the country.
The agency issued a ground stop order after its NOTAM (or Notification of Air Tasks) system malfunctioned. The FAA lifted the order shortly before 9 a.m. ET, and the agency said normal air traffic operations were resuming nationwide. It said it was still trying to determine the cause of the problem.
But airlines continue to delay or cancel flights due to persistent congestion. An airline source familiar with the situation said airlines may implement plans for ground delays, which could lead to further schedule issues.
As of 9:40 a.m. ET, the FAA’s website still showed ground stops at Atlanta, Boston and New York’s LaGuardia. The site also showed ground delays at Charlotte Douglas International Airport in North Carolina, one of American Airlines’ largest hubs.
The cause of the outage is unclear
US President Joe Biden said there was no immediate information on what caused the outage – the second US aviation crisis in as many weeks. He said he had been briefed on the situation and was in touch with Transportation Secretary Pete Buttigieg.
“I just spoke to Buttigieg,” he told reporters as he left the White House. “They didn’t know what the reason was. But I was still on the phone with him for the last 10 minutes. I let them know and reported directly to me. The plane can still land safely, it just can’t take off now.”
He continued, “They don’t know what caused it. They expect to have a clear idea of what caused it within a few hours and will respond at that time.”
Asked whether it was a cyberattack, Biden said: “They don’t know. They’ll find out.”
Earlier, White House press secretary Karin Jean-Pierre said in a statement that “there is currently no evidence of a cyber attack,” but Biden has ordered the Department of Transportation to investigate.
Buttigieg said via Twitter Wednesday morning that he had ordered a “postmortem to determine root cause and recommend next steps.”
thousands of delays
FlightAware, which tracks delays and cancellations, showed that as of 9:25 a.m. ET, about 4,600 flights to, from, and within the U.S. were delayed, and more than 800 flights had been canceled so far.
Southwest Airlines canceled tens of thousands of flights after Christmas after the system crashed, more cancellations and delays than any other airline. About 8% of Southwest’s flights were canceled and 42% were delayed.
Still, international flights to the US continue to depart from Amsterdam and Paris. A spokesman for Schiphol told CNN that “a workaround has been issued” and that flights are still departing from Amsterdam.
Paris-Charles de Gaulle has not canceled any flights, but delays are expected, according to the airport press office. Frankfurt Airport also told CNN it was not affected.
A spokesman for London’s Heathrow Airport told CNN they were “not aware of any flight cancellations and flights to the US have recently departed”, but passengers have reported significant delays.
Shabnam Amini told CNN she and other passengers boarded American Airlines Flight 51 to Dallas for nearly three hours at Heathrow because of the FAA shutdown.
She said they were told there was a delay but boarded the plane anyway.
Commercial airline pilots use NOTAMS to obtain real-time information on flight hazards and restrictions. The FAA states that NOTAMS cannot be used as the sole source of information, so some flights may be able to meet safety requirements by using other data.
Wednesday’s incident follows another aviation crisis. A massive winter storm during the year-end holiday season caused widespread disruption and helped spark the Southwest Airlines collapse, affecting thousands of passengers.
– This is a developing story. It will be updated.
CNN’s Barry Neild, Paul P. Murphy, Betsy Kline, Livvy Doherty and Stephanie Halasz contributed to this story.