Cross-border flights resume after U.S. ground stop

Flights between Canada and the United States began moving again Friday night. The U.S. Federal Aviation Administration (FAA) lifted a rare nationwide ground stop that had halted every departure from American airports for more than four hours. NAV CANADA, which runs Canada's civil air navigation system, confirmed the stop was over shortly before 9 p.m. Eastern time. It warned that some delays could last while operations return to normal, and told passengers to check their flight status with their airline.

The FAA ordered the stop shortly before 4 p.m. Eastern, citing communication problems at several of the regional centres that control high-altitude air traffic. U.S. Transportation Secretary Sean Duffy told reporters the stop was lifted at 8:15 p.m. Eastern.

Canadian airports halt U.S. flights

NAV CANADA's own systems were not affected, but Canadian travellers were hit hard because so much cross-border traffic stopped at once. At Toronto Pearson, all U.S.-bound departures and arrivals were halted. More than 120 U.S. flights were cancelled, according to the airport's website, and a spokesperson told CP24 that another 20 international flights were also cancelled. Domestic and international flights that did not pass through U.S. airspace kept operating.

Air Canada cancelled all of its flights to and from the U.S. for the rest of Friday. It warned that flights between Canada and the Caribbean or South America that cross U.S. airspace could also be affected. Porter Airlines cancelled its remaining U.S. flights for the day out of Toronto's Billy Bishop airport and said disruptions could continue through the weekend. WestJet said it was following the regulator's directions.

Vancouver, Calgary, Edmonton and Montréal-Trudeau were also affected. At Vancouver International, Air India paused check-in because of what it called an "evolving airspace issue" over the United States, The Globe and Mail reported. Airports with no U.S. flights scheduled for the rest of the day, including Saskatoon and Regina, reported no disruption, and Halifax said one flight to Boston was delayed.

During the evening, NAV CANADA briefly applied "traffic management measures" at Pearson, Montréal-Trudeau, Calgary and Vancouver to control the volume of traffic. It lifted them before the U.S. stop ended.

Ottawa offers help

Transport Minister Steven MacKinnon said Canada's systems were operating normally and that the government was in contact with NAV CANADA. According to The Globe and Mail, he said Canada had offered the FAA whatever help it needed, including letting U.S.-bound aircraft land in Canada. His office could not say whether any such request had been made.

What caused it

The cause is still being investigated. Duffy told reporters that network switches and routers "got overloaded with data," which made radar and communications unreliable, though not completely lost. He also blamed the aging U.S. air traffic control system and asked Congress for emergency funding. Homeland Security Secretary Markwayne Mullin told reporters there was "no indication as of yet that this was a nefarious attack." He said the problem was not linked to a Microsoft outage that began a day earlier, but he did not rule out a cyberattack.

Air Space Intelligence, the company behind an AI-assisted traffic management tool the FAA expanded to all its control centres earlier this week, said its system did not cause the stop.

Thousands of flights were cancelled or delayed across the United States, and other countries, including Mexico, held U.S.-bound aircraft on the ground. It was only the third nationwide ground stop in U.S. history, after the Sept. 11, 2001 attacks and a system outage in January 2023 that lasted less than two hours.

Airports advised travellers not to come to the airport without a confirmed booking, and to check with their airline before leaving home over the weekend.

Sources: NAV CANADA on X