Updated March 21, 2025 at 14:18 PM ET
LONDON — Europe's busiest airport announced it will reopen for a small number of flights late Friday, after an overnight power shutdown forced dozens of flights to divert in midair and disrupted travel for passengers worldwide.
In a message on social media, Heathrow airport said it was "now safely able to restart flights, prioritising repatriation and relocation of aircraft."
The statement instructed passengers not to travel to the airport unless specifically told to do so by their airline.
The London Fire Brigade said it had received more than 200 calls from concerned residents about a vast conflagration that began late Thursday at a high-voltage substation close to the airport, where a transformer that contained 25,000 liters — about 6,600 gallons — of cooling oil was fully alight.
The fire knocked out power to 16,000 homes as well as Heathrow, west of London, just hours before the airport was due to open at 6 a.m. local time.
More than 1,000 flights were diverted or canceled over the course of the day, delaying hundreds of thousands of passengers, with some returned to their points of origin or routed via third countries.
London's Metropolitan police have said there's no indication of foul play so far, but its counterterrorism command is involved in an investigation into the fire's origins.
Several fire engines and dozens of firefighters battled the blaze in the nearby town of Hayes, while an airport spokesperson warned passengers to avoid any transit to Heathrow.
Video uploaded to social media sites showed a vast conflagration at the substation facility, with the London Fire Brigade saying residents were concerned about the significant amount of smoke emanating from the site. More than 100 people were evacuated from their homes since the first emergency calls were made late Thursday.
More than 100 flights en route to Heathrow have been diverted, according to data from the flight tracking website Flightradar24, with United landing one flight from New York in Shannon, Ireland, and Australian carrier Qantas diverting two planes to Paris.
United said seven of its scheduled flights had returned to their airports of origin, the Associated Press reported, while another flight tracking website, FlightAware, showed both Delta and American had canceled flights from New York's John F. Kennedy International Airport.
Dozens of international airlines will be forced to reconfigure their flight networks, calling up aircraft, crew and pilots in other locations to avoid further cancellations in the coming days. The impact for British Airways, which uses Heathrow as its largest hub, has been seismic.
"We expect significant disruption over the coming days," said a Heathrow spokesperson in a public statement early Friday, adding that "passengers should not travel to the airport under any circumstances until the airport reopens."
In its announcement later that some flights were resuming, the airport said its teams "worked tirelessly since the incident to ensure a speedy recovery."
Heathrow typically hosts around 200,000 passengers a day, with transatlantic travel to the United States responsible for a sizeable portion of those passenger numbers. The British government recently approved plans to build a third runway at Heathrow to help boost economic growth.
The U.K. rail company, National Rail, has stopped all trains to Heathrow, while more than 16,000 homes in the surrounding area have also lost power, according to local provider Scottish and Southern Electricity Networks.
In 2023, a problem with the U.K.'s air traffic control system caused similar delays at several U.K. airports, forcing landings and takeoffs to be spread out on what was then one of the busiest travel days that year.
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