US flight halt lasted four and a half hours after air traffic communications failure

What happened

The Federal Aviation Administration ordered all departures from US airports to stay on the ground on Friday, 13 November, at around 20:30 Lisbon time. A Reuters report cited by Observador said Eurocontrol also halted departures from Europe to the United States at the FAA's request. Aircraft already in the air were allowed to land, while international flights were to be handled case by case. The order was lifted at 01:30 on Saturday, 14 November, after roughly four and a half hours, according to PÚBLICO.

What caused the failure

Observador, citing aviation reporter Jon Ostrower of The Air Current as quoted by The Guardian, reported that the FAA's Washington command centre was alerted at 15:30 local time that several air traffic control centres had lost communications, radio frequencies and radar. The breakdown began at the Chicago route control centre and spread within minutes to Boston, Washington, New York and Minneapolis. The agency's first statement cited "extraordinary circumstances and security reasons" without technical detail.

At a White House press conference after the lifting, Transportation Secretary Sean Duffy and Homeland Security Secretary Markwayne Mullin pointed to an overload of data on old equipment after new technology had been introduced. Duffy described analogue telecommunications in which switches and routers were overwhelmed and began producing data inconsistencies, which forced the system to shut down. He said the newer IP switches had not failed and tied the problem to a shortfall in congressional funding, saying President Donald Trump had requested the money to replace the old hardware. Duffy denied any link to Smart, an AI-based air traffic tool announced three days earlier.

Flights and passengers

FlightAware, cited by PÚBLICO, recorded 6,999 delayed and 9,122 cancelled flights to and from the United States on Friday. Its figures reported on Saturday showed 780 delays and 3,273 cancellations as the effects continued. Other counts measure different things: Observador, citing FlightRadar24 via Lusa, reported more than 2,400 cancellations in the United States, while SIC put cancellations worldwide at six thousand and said hundreds of thousands of passengers were affected. SIC also described the stoppage as the longest halt to US flights since the 11 September attacks, 25 years ago.

Delayed, Friday 13 November6,999

Cancelled, Friday 13 November9,122

Delayed, Saturday 14 November780

Cancelled, Saturday 14 November3,273

Delayed, Friday 13 November

6999 flights

Cancelled, Friday 13 November

9122 flights

Delayed, Saturday 14 November

780 flights

Cancelled, Saturday 14 November

3273 flights

Data from the article text

Observador reported that the halt did not affect any flight to or from Portugal. TAP told RTP it was following the instructions of US authorities for aircraft in flight and had other aircraft parked at US airports. An Azores Airlines flight from Boston reached Ponta Delgada at 06:30 on Saturday, only half an hour late. Jorge Roquette, director of Cascais Airport, said in an SIC Notícias interview that he expects several days to pass before normal operations return at US airports.

“It lost radar and radio telecommunications, two things that are absolutely vital to ensuring safety in the air.”

Cyberattack and a separate outage

PÚBLICO reported there were no signs of a cyberattack. The FBI is examining whether a software update lay behind the failure and has ruled out any crime. Mullin said at the press conference that there was zero evidence of hacking and that the problem appeared to be mechanical.

Expresso described a Microsoft failure on Thursday, 12 November, that left millions of Outlook 365 users unable to send or receive email and also affected Teams. The newspaper treated it as a separate incident from the air traffic outage and noted that both problems are now resolved, while the explanations offered describe effects rather than causes.

Reaction and next steps

Mullin told reporters that the public was never in danger, that no lives or flights were at risk, and that he understood the conspiracy theories circulating online. He said Americans' loved ones were safe and hoped operations would soon return to normal. Duffy asked Americans whether they wanted Congress to fund the replacement of the old equipment.