US lifts nationwide ground stop after air traffic communications failure

The US Federal Aviation Administration lifted a nationwide ground stop on Friday evening after a communications failure at air traffic control centres halted flights across the country for about four hours, the longest nationwide grounding since the September 11, 2001 attacks.

Transportation Secretary Sean Duffy said US airspace reopened at 8:15 pm Eastern Time (0115 GMT). Departures would resume gradually, he said. "It's going to be slow," Duffy told reporters at the White House.

Flight tracking service FlightRadar24 counted more than 6,600 flights cancelled and 8,600 delayed, with another 1,500 already cancelled for Sunday, according to the Kathmandu Post and Rappler, which carried detailed accounts of the day. Aviation analysts quoted in those reports said airline schedules could take days to restore.

Duffy said the trouble began at 3:36 pm, when air traffic control centres saw instability in radar and communications systems. "Our switches, our routers actually got overloaded with data, and they started to give us inconsistencies in the data from those routers, and because of that we shut the system down," he said. Radar and communications were never completely lost, he said, and controllers landed thousands of planes safely.

Duffy said he and Homeland Security Secretary Markwayne Mullin met President Donald Trump in the Oval Office to discuss the outage. Mullin said there was "zero evidence" it resulted from a cyberattack or a rogue artificial intelligence system, though investigators had not ruled out either. "It appears this was mechanically driven, however, we're still looking," he said. The National Security Agency was working with the Department of Homeland Security on the investigation.

Two airline officials said the outage appeared to affect a telecommunications network overseen by L3Harris Technologies, which handles radio frequencies controllers use to talk to pilots. The company did not respond to a request for comment.

Duffy blamed Congress for not funding a replacement system and called for $50 billion to modernise it. Earlier on Friday, before the outage, the White House and the Department of Transportation had urged Congress to approve $30.1 billion to upgrade airports and air traffic infrastructure. "What we have is an incredibly old air traffic control system," he said.

Passengers were stranded overnight at airports from Boston to Seattle. Edward Kargbo, 50, of West Chester, Pennsylvania, had been due to take a 9 pm Ethiopian Airlines flight to Lomé, Togo, and planned to sleep at the airport before a rescheduled 6 am flight. "I have to squat the night here," he said. "I'm stranded." Louise Maher, 47, whose British Airways flight to London was caught at Newark, said: "I might cry at some point but not yet."

US airlines will not be required to compensate stranded passengers because the carriers were not responsible for the FAA failure. Shares in American, United and Delta fell between 1 and 2 percent in after-hours trading, and JetBlue dropped about 3 percent. American said it was prioritising flights to smaller cities and international destinations to reposition aircraft and crews. The only other nationwide ground stop since 2001 came in January 2023, when the FAA halted domestic departures for about 90 minutes.