Flights in the US have slowly started resuming after being grounded for several hours on Friday due to a major communications outage, but authorities have warned that a return to normal operations will take time.
The Federal Aviation Administration (FAA) lifted a nationwide ground stop about four hours after it was declared on Friday afternoon, delaying or canceling more than 11,000 US flights, according to aviation tracker FlightAware, and throwing airports into sudden chaos.
The FAA confirmed the airspace was open in an advisory on its website. “So at 8.15 tonight, Eastern Time, we've opened up the airspace,†Sean Duffy, the US transportation secretary, said. “But it's going to take us some time to unwind what's happened this afternoon.â€
Duffy said the federal government had “identified the problem†that brought down the US air traffic control system on Friday and the system “is operational right nowâ€.
At a White House briefing on Friday evening, Duffy said the trouble began at 3.36pm, when air traffic control centres experienced ​instability in radar and communications systems.
“What we have is an incredibly old air traffic control system,†he said. “Our routers actually got overloaded with data, and … they started to give us inconsistency in the data from those routers. And because of that, we shut the system down.â€
But the briefing on Friday evening with Markwayne Mullin, the homeland security secretary, quickly turned into a plea for funding from Congress to “fully fund a full build of a brand new air traffic control systemâ€.
A notice from the FAA had earlier said the ground stop was imposed “due to extraordinary circumstances and for reasons of safetyâ€.
Duffy said more than 3,500 airplanes were in the air when the ground stop was issued.
Mullin said in a news conference that preliminary investigations into the stoppage did not indicate that it was tied to a “nefarious attackâ€.
“There's no indication as of yet that this was a nefarious attack against it. It's just a telecommunications outage as of right now,†he told reporters.
The flight grounding caused widespread chaos and left hundreds of thousands of passengers in limbo. Footage from airports around the country showed gates full, with planes waiting on taxiways. Passengers thronged concourses, desperate for information about an outage that had thrown their plans into chaos.
As news of the airspace reopening trickled down to airline passengers on Friday evening, not all greeted the news with joy. A woman at John F Kennedy airport in New York who gave her name as simply Lola said she was frustrated. She had already rebooked her flight to Atlanta for another day and was going home. “I don't like it,†she said.
Amid the earlier confusion at US airports, the California governor, Gavin Newsom, called the Trump administration to offer more clarity to passengers who are trying to get to their destinations.
“Americans are stuck at airports across the country. They deserve answers, clear updates, and a plan to get home safely. Instead, the Trump Administration is correcting reporters on AI's “preferred nameâ€. These are not serious people,†Newsom wrote in a post on X, in reference to Mullin correcting a reporter's use of the term AI earlier in the day.
In an interview on CNN, US congressman Ro Khanna said that he is waiting to be briefed on what exactly led to the technical issues and sparked the ground stoppage and for more public-facing communications from the transportation secretary.
“There's a lot of nervousness,†Khanna said of the feeling among passengers. “We're waiting to be briefed in Congress about what, exactly, has happened. We just need communication from them. If they were there every hour briefing the American public, it would help and give us a sense of a timeline.â€
According to CNN, the FAA told airlines that the outages are the result of router malfunctions that are believed to have originated at Chicago Midway international airport and rippled across the rest of the US.
The FAA said in a statement that they “thoroughly tested†their systems to confirm they were stable and reliable before clearing flights to resume.
San Francisco international airport announced in a social media post that flights bound for Hawaii and Asia were cleared to depart.
John F Kennedy airport posted on its social media that travelers should confirm flight status with the airline before heading to the airport.
US airlines including United, Delta, Southwest and American Airlines announced they were resuming flights on Friday night after the ground stop was lifted.
United said it was restarting operations, “including some Friday night flightsâ€, while American Airlines said it was focused on “operating as many remaining flights as possible this eveningâ€.
British Airways cancelled a flight to New York that had been due to take off from Heathrow at 10.30pm on Friday night, and a spokesperson for Manchester airport confirmed three US-bound flights scheduled to leave on Saturday morning – all operated by Virgin Atlantic – were likely to be affected if the issue was not resolved soon.
A ground-stop order by the FAA requires that aircraft remain on the ground and bars them from taking off. Planes already in the air are usually allowed to remain in the air.
This is the third time all departing flights have been grounded in the US. The first time was on 11 September 2011; the other was in January 2023, when the FAA paused all â domestic departures for less than two hours after a pilot notification system malfunctioned.
The FAA has more than 14,000 air traffic controllers who handle the more than 44,000 flights that take off from airports across the US each day, according to FAA data.
Last week, the FAA announced that the first digital air traffic control towers in the US were officially operational in Alaska and Florida, as part of a modernization project intended to reduce flight delays and improve the flow of air traffic.
Last year, ​Congress ​approved $12.5bn to fix ​the FAA's ageing communications system, and ​on Friday ‌the FAA ​and ​White House asked Congress for another $30.1bn to address other issues.
