Power Outage Shuts Heathrow, Snarling Global Air Travel

The power outage was caused by a fire at an electrical substation supplying the airport, according to Heathrow.

“We expect significant disruption over the coming days and passengers should not travel to the airport under any circumstances until the airport reopens,” a spokesperson said, adding that it isn’t clear when power will be reliably restored.

About 120 aircraft were en route to Heathrow when the fire broke out, leading to a power cut at the airport, according to aircraft tracking specialist Flightradar24. Those flights have been diverted. 

A flight from Tokyo was sent to Helsinki, a departure from Hong Kong was diverted to Amsterdam and one from Dubai was rerouted to Munich. From the U.S., flights from Atlanta, Boston, New York were diverted to Shannon Airport in Ireland, others were turned around, and one from Dallas was sent to Bangor, Maine.

In total, more than 1,300 flights had been scheduled to arrive at or depart from the hub on Friday, according to Flightradar24. Many more are expected to be disrupted, including into the weekend, as aircraft are left out of position and flight schedules are rearranged to accommodate those disrupted.

Stella Schuhmann, an 18-year-old university student in Regensburg, Germany, had tickets to see her favorite singer, FKA twigs, in concert Friday night in London with her best friend. When her mother woke her up in the morning to tell her their flight to Heathrow was canceled, she cried. 

“It’s kind of crazy. It’s one of the biggest airports in the world,” she said. “Why don’t they have backup?”

The fire broke out late Thursday evening at a substation in western London, according to the London Fire Brigade. Around 70 firefighters were battling the fire early Friday, which also cut power to tens of thousands of homes and local businesses.

“There was a backup generator but that was also affected by the fire, which gives a sense of how unusual and unprecedented it was,” Ed Miliband, the U.K.’s energy minister, told Sky News. A second backup was being brought online to try to restore power, he said. 

In a separate interview with LBC radio, Miliband said the initial indications from the chief executive of the utility National Grid were that the incident was an accident.

“There’s no suggestion that there is foul play,” Miliband said. “At the moment the focus is on restoring the power, we don’t yet have a real understanding of what caused the fire.”

Smoke was still rising from the substation Friday morning, with an acrid smell in the air. Surrounding streets were cordoned off by police and fire officers.

European leaders are on edge, wary of potential acts of sabotage amid the war in Ukraine and tensions with Russia. The head of the U.K.’s domestic spy agency, MI5, warned last year that the Kremlin’s spy agencies were on a “sustained mission to generate mayhem” across Europe, including encouraging arson and sabotage.

Heathrow was the fourth-busiest airport in the world last year ranked by capacity, according to data provider OAG. Last year, 83.9 million passengers traveled through the hub, according to the airport.

While aircraft were diverted to alternative airports around the world, many were rerouted to land elsewhere in the U.K., predominantly at London Gatwick.

At Gatwick, a steady stream of tired-looking passengers were coming out of arrivals with LHR baggage tags on large suitcases. Several passengers said they only found out where they would be landing toward the end of their long-haul flights.

British Airways is the biggest operator at Heathrow and was scheduled to fly approximately 341 flights into the hub on Friday, according to aviation data specialist Cirium. That’s by far the most of any airline, accounting for more than half of affected arrivals. 

BA, which has a joint venture with American Airlines on trips across the Atlantic, is one of the biggest carriers of passengers between the U.S. and Europe.

“London Heathrow Airport will be closed until further notice,” British Airways wrote in a letter to passengers set to travel on Friday, without specifying how long flights would be delayed. It apologized for the disruption.

Virgin Atlantic had the second-most scheduled arrivals, with 31, and Lufthansa the third-most with 21, Cirium said. American Airlines, United Airlines and Delta had been scheduled to fly a combined 45 into Heathrow on Friday. 

While large-scale closures of major airports are rare, they do happen—and it can take days to get operations back to normal. 

Heathrow last suffered major disruption in the post-lockdown summer of 2022 when staff shortages led to a rash of delays and cancellations, prompting the airport to impose a monthslong cap on daily passenger numbers. And in December 2018, Gatwick, London’s secondary airport, repeatedly suspended flights after reports of unauthorized drone activity in the area. 

Derek Kramer, a 36-year-old teacher, was scheduled to fly back to Indiana on Friday after a weeklong vacation in London with his wife and two children. He and his wife, who is also a teacher, have found a flight returning Monday morning, meaning they are set to miss their first day back at school after the spring break.

“We were hoping to get back and then have a couple days to relax,” Kramer said. 

Now, the couple is scrambling to find a place to stay this weekend and hoping he can be reimbursed for the additional expenses.

“We’re just crossing our fingers,” he said.

Write to Hannah Miao at hannah.miao@wsj.com and Benjamin Katz at ben.katz@wsj.com