London5:03 p.m. March 21
The cause of a giant blaze that knocked out power to one of the world’s busiest airports was under investigation. Diverted flights were to be the first to arrive, but analysts said the chaos could last days.
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transcript
We’ve had a catastrophic fire at an electricity substation. We don’t know the cause of this fire. It’s obviously an unprecedented event. But if we don’t get one today, should we assume that we’ll get one tomorrow? “Tomorrow? After tomorrow?” So you don’t know.
Megan SpeciaLynsey ChutelMichael D. Shear and Eshe Nelson
Reporting from London
Heathrow Airport in London said some flights would resume later on Friday after a fire caused a power outage that shut down operations and disrupted travel for tens of thousands of people at one of the world’s busiest air travel hubs.
An airport spokeswoman said officials hoped that Heathrow would be fully operating by Saturday, after the shutdown caused ripple effects around the world and was expected to cause delays throughout the weekend.
“Our first flights will be repatriation flights and relocating aircraft,” the spokeswoman said. “Passengers should not go to the airport before checking with their airline. We will now work with the airlines on repatriating the passengers who were diverted to other airports in Europe.”
The outage raised questions about the resilience of Britain’s largest airport and why it appeared to be so reliant on a single electrical substation where a large blaze broke out overnight. As many as 290,000 passengers could be affected by the closure, according to Cirium, an aviation data company.
Britain’s National Grid said on Friday afternoon that it had reconfigured its network to partly restore power at Heathrow on an interim basis. The London Fire Brigade said in the afternoon that 10 percent of the fire was still burning but that it was under control.
London’s Metropolitan Police said their counterterrorism specialists were leading the investigation into the cause of the fire, “given the location of the substation and the impact this incident has had on critical national infrastructure.” But the city’s mayor and other officials said there was no immediate indication of foul play.
A Heathrow representative said in a statement that significant delays would be expected in the coming days.
Here’s what else to know:
Substation fire: The fire at the North Hyde electricity substation was under control, the London Fire Brigade said around 6:30 a.m. local time. About 150 people were evacuated from the area around the substation after the fire broke out late Thursday. The energy company National Grid said that about 4,900 customers were without power as of Friday morning. There were no reports of injuries, officials said.
Airlines scramble: About 80 airlines operate at Heathrow, and they diverted inbound flights to other airports in Britain and elsewhere in Europe, or sent them back to their origin while scrambling to rebook journeys. The worst-affected airline was British Airways, which had about 340 flights scheduled to land at Heathrow on Friday, according to data from Flightradar24.
Heathrow scene: Police and emergency vehicles were parked at the otherwise deserted drop-off zone outside one terminal, and airport employees turned away travelers. Airline counters stood empty, digital flight information screens were blank, passageways were dimly lit by emergency lighting, and escalators stood still — an eerie scene at the usually bustling airport.
By the numbers: Heathrow has two runways and four terminals serving more than 230 destinations in 90 countries. Last year, about 83.9 million passengers and 1.7 million tons of cargo were flown through the hub.
Eshe Nelson
British Airways says eight of its long-haul flights will depart from Heathrow this evening. In an emailed statement, it said some customers can make their way to the airport.
Eshe Nelson
The resumed service will include certain flights to Johannesburg, Singapore, Riyadh, Cape Town, Sydney and Buenos Aires. Travelers on the rescheduled flights are being contacted, the airline said.
Christine Chung
A spokesman for United Airlines said that most of the airline’s 17 scheduled flights to Heathrow Airport are expected to operate on Friday. These departures are scheduled for late Friday evening, arriving at Heathrow on Saturday morning.
Flight cancelled or rerouted? Travel plans altered? Shipments delayed? We would like to hear from you.
By The New York Times
Jenny Gross
Reporting from London
The closure of London’s Heathrow Airport on Friday comes 15 years after one of Europe’s most severe air travel disruptions, when the Eyjafjallajökull volcano erupted in Iceland, sending ash miles into the sky and disrupting travel for millions, including at Heathrow.
The ash cloud grounded more than 100,000 flights over nearly a week in April 2010 as it drifted across Northern Europe, including the English Channel. Passengers slept on airport cots as customer service lines became overwhelmed. Others sought alternative routes by train or rental car as disruptions lasted for weeks.
The airline industry’s losses were estimated at $1.7 billion, according to the International Air Transport Association, which represents airlines.
The eruption led to the worst disruption in international air travel since the attacks of Sept. 11, 2001, when all air travel in and out of the United States was halted for three days.
The ash drifted to between 18,000 and 33,000 feet above the earth, altitudes commonly used by commercial jetliners, and flying around the ash was not an option because it covered such a large area. The guidance from the International Civil Aviation Organization at the time was clear: “In the case of volcanic ash, regardless of ash concentration — avoid, avoid, avoid.”
Volcanic ash poses particular threats to aircraft because it is primarily made up of abrasive silicate particles, which can damage jet engines.
The Civil Aviation Authority in Britain said then that volcanic eruptions typically happen in areas where air traffic is light and airspace is not congested. “There was no precedent for this type of situation,” the agency said of the Eyjafjallajökull eruption.
Megan Specia
Some flights at Heathrow will resume later today, a spokeswoman said, adding that officials hope the airport will be fully operational by tomorrow. “Our first flights will be repatriation flights and relocating aircraft,” she said. Passengers should not go to the airport before checking with their airline. “We will now work with the airlines on repatriating the passengers who were diverted to other airports in Europe.”
Shayla Colon
John Connor, 22, sat at Newark Liberty International Airport on Friday, waiting in vain to get home to England after backpacking abroad for two years. “We sat on the plane for about five hours before they said the flight was called off,” he said. “I’m trying to get a plane somewhere close — Paris, Dublin, anywhere else,” he added. “We’re being told straight up no.”
Eshe Nelson
The chief executive of British Airways, Sean Doyle, warned that Heathrow Airport’s closure would have “a huge impact” on the airline’s customers over the coming days. British Airways was due to operate more than 670 flights carrying around 107,000 customers on Friday, and similar numbers were planned over the weekend, he said. “We have flight and cabin crew colleagues and planes that are currently at locations where we weren’t planning on them to be,” he said.
Eshe Nelson
Adding to the complexity, Doyle said, is that there are legal restrictions to how long crews can work. “That means even if things do get back up and running soon, we will have the logistical issue of getting new crews out to operate those aircraft,” he said.
Christopher Maag
Only a few British Airlines passengers remained camped out at Kennedy Airport’s Terminal 8 on Friday morning. After making new travel arrangements, some waited for cars to take them to nearby hotels. Others said they planned to spend all day Friday in the terminal.
Stephen Castle and Megan Specia
Britain’s counterterrorism police are leading the investigation into the cause of the fire near Heathrow Airport, signaling that the possibility of sabotage was being taken seriously, at least as a precaution. But officials said there was no immediate evidence that foul play was involved.
After the blaze at the electrical substation and subsequent power outage, the scale of the resulting chaos raised uncomfortable questions for Britain’s government about the security measures protecting key transport hubs and the resilience of the country’s aging infrastructure.
The Metropolitan Police in London said that counterterrorism specialists had taken charge “given the location of the substation and the impact this incident has had on critical national infrastructure.”
Sadiq Khan, the mayor of London, said it was “not unusual” for the specialized officers to be involved in an investigation of such a major incident, and he told Sky News that there was “no reason at all for anyone to be concerned or alarmed.”
With the fire under control but still burning, nonetheless, nothing has been ruled out.
In a statement, Prime Minister Keir Starmer said he was “receiving regular updates” about the situation at Heathrow and was “in close contact with partners on the ground.” He added that he knew the outage was “causing distress and disruption, especially for those traveling or without power in their homes.”
A spokeswoman for Heathrow said on Friday afternoon that some flights would resume later in the day, adding that officials hoped the airport would be fully operational by Saturday.
John McDonnell, a lawmaker who represents Hayes, the area where the fire broke out, said on Friday afternoon that any investigation would need to look at “why backup arrangements have not worked” and how the infrastructure could be so vulnerable.
“There are lessons that have got to be learned here,” he told reporters.
Ivan Penn
Electrical substation fires of the kind that shut down London’s Heathrow Airport on Friday happen for a variety of reasons and can leave many people without power. But they are rare, an energy expert said.
“While we can’t speak specifics about this fire, some causes could include equipment failures, lightning strikes, and animal encroachment,” Andrew Phillips, the vice president of transmission and distribution infrastructure at the Electric Power Research Institute, an nonprofit energy research and development institute in Palo Alto, Calif.
The London Fire Brigade and the London Metropolitan Police were investigating the cause of the fire. The blaze began in “a transformer comprising 25,000 liters of cooling oil that was fully alight” at the electric substation near Heathrow Airport, said Jonathan Smith, the deputy commissioner for the fire brigade. The fire caused the airport to lose power, forcing the cancellation of hundreds of flights.
Security of electrical grids have been a growing concern of governments across the world.
In the United States, electrical substations have been the target of attacks by gunmen, who caused tens of thousands of people to lose power in North Carolina, Oregon and Washington in late 2022 and early 2023.
Those shootings included two attacks on substations in Moore County, N.C., in December 2022, caused 45,000 people to lose power some for five days.
Experts have said that the shootings were inspired by a sniper attack in 2013 on a power station in California. That incident began to raise alarms across the electricity industry about the safety of substations. Some of the recent U.S. substation attacks have been linked to white supremacists.
Substations serve as connection and distribution points in the electrical grid. High-voltage transmission lines bring electricity from power plants, some hundreds of miles away, to substations that reduce voltage so the electricity can be distributed to homes and businesses.
Loss of substations can severely disrupt electrical service because each one can serve tens of thousands of homes and businesses. Some larger substations feed energy to smaller substations.
Megan Specia contributed reporting.
Lynsey Chutel
In Hayes, the neighborhood surrounding the power station where a fire broke out near Heathrow Airport late Thursday, electricity had returned by Friday afternoon, the blaze was under control and most stores had reopened on the high street.
Most of the 150 residents who were evacuated from their homes around the North Hyde electrical substation had left the area, officials said. A few people had come into the library to charge their devices. Roads around the power station remained cordoned off, and a helicopter hovered above.
On a street behind the police cordon, Nesh Khan returned to his home around midday, after leaving early Friday morning. On Thursday night, he said, he heard two loud bangs and looked outside to see “a massive ball of flame and a massive cloud of smoke going all over.”
With thick, sooty smoke hanging in the air as firefighters battled the blaze, he said, he and his wife decided to leave with their infant son before evacuation instructions came.
Another resident, Navdeep Saggi, did not evacuate the home he shares with his parents, his wife and two young children. He kept the doors and windows closed, as authorities advised, even as the smoke had cleared by Friday afternoon.
On Thursday night, he said he was awakened by a loud bang, and a flurry of messages and calls from a neighborhood group. Behind his home, he saw flames from the power station burning higher than a three-story warehouse next door.
Britain’s National Grid said on Friday afternoon that the network of the North Hyde substation “has been reconfigured to restore all customers impacted,” and apologized for the disruption.
“We are continuing to work closely with all stakeholders to manage this incident, and are focused on returning to normal resilience levels as soon as possible.”
John McDonnell, the lawmaker who represents Hayes, said that any investigation of the fire will need to examine “why backup arrangements have not worked” and how the affected infrastructure was so vulnerable.
“There are lessons that have got to be learned here,” he told reporters on Friday afternoon.
Megan Specia and Claire Moses contributed reporting.
Niraj Chokshi
Reporting on aviation
Airlines, airports and air traffic controllers prepare for chaos. But that doesn’t make responding to it any less complicated.
The global aviation system is deeply interconnected and responding to a disruption — especially one as severe as the power outage at London’s Heathrow Airport, a global hub — is a delicate balancing act. For airlines, moving even a small number of flights can have cascading effects.
Heathrow was closed Friday after a fire at a nearby power substation, leaving tens of thousands of travelers, and dozens of airlines, facing cancellations, rerouted flights and a cascading series of changes to schedules.
“They’re thinking not just in terms of a single day, but recovery,” said Dr. Michael McCormick, a professor of air traffic management at Embry‑Riddle Aeronautical University, who managed the federal airspace over New York during the Sept. 11 terrorist attacks. “They have to look at where passengers with bags, aircraft and aircrews need to be tomorrow, the next day, and the next day.”
When crises occur, airline network operation centers go into overdrive. The centers are the nerve centers of carriers — typically large, quiet, secure rooms with power backups and protections against severe weather and disasters.
At large airlines, operations centers are staffed around the clock with teams that monitor the weather, manage planes, communicate with air traffic control, schedule crews and much more.
Small disruptions can be handled surgically — a sick pilot can be replaced or a broken plane swapped out for another. But bigger disruptions like the one at London’s Heathrow Airport can require scrapping and reworking intricate plans while taking into account a wide range of limitations.
Planes differ in how many people they can carry and how far they can fly, so a small plane used for shorter domestic flights cannot easily be swapped in for a larger one used on longer flights. They also must be fueled adequately and their weight balanced appropriately, needs that must be adjusted if planes are rerouted.
Regulations require that pilots and flight attendants are not overworked and are allowed to rest after certain number of hours on the clock. If a flight takes too long to depart, a crew can time out. When schedulers do reassign crews, they also have to take into account where those pilots and flight attendants are needed next, or they could risk more disruptions later.
Airlines, of course, do not operate in isolation. As they change plans, they need to work with airport and air traffic control officials who may have limited resources to accommodate the changes. Airports are limited not just in how many flights they can receive, but also, in some cases, what types of planes they can safely accept. In the United States, for example, many air traffic control towers have long suffered from controller shortages.
Christopher Maag
Of the eight flights scheduled to leave Kennedy International Airport for Heathrow on Friday, five have already been canceled, according to departure boards at Kennedy. All eight arriving flights from Heathrow were canceled.
Megan Specia
Britain’s National Grid said the network of the North Hyde substation, where the fire knocked out power, has been reconfigured to restore power on an interim basis to the parts of Heathrow Airport that are connected to it. “This is an interim solution while we carry out further work at North Hyde to return the substation and our network to normal operation,” the power company said.
Megan Specia
Sadiq Khan, London’s mayor, speaking to Sky News, stressed that it was “not unusual” for counterterrorism police to be involved in an investigation of a major fire like the one that cut the power at Heathrow Airport, adding, “there is no reason at all for anyone to be concerned or alarmed in relation to the fire at the substation.”
Lynsey Chutel
James Porritt, from Dorset, England, drove up with his wife Thursday night to stay at a hotel at Heathrow. They had planned to catch an early flight to Brisbane, Australia, but woke up to find that the airport was closed.
Michael D. Shear
Heathrow Airport has released a statement that says restoring electricity to the facility will take time. While the airport has “multiple sources of energy,” there is no backup that can power the entire airport, which “uses as much energy as a small city,” it said.
Michael D. Shear
Amid questions about how the electricity substation fire near the airport caused it to lose power, Heathrow’s statement said that that backup systems, including diesel generators, did kick in. Those backups would have allowed planes to land, but would not have allowed the airport to operate fully, it said.
Eshe Nelson
British Airways said it would give customers booked to fly to or from Heathrow over the weekend the option to rebook on a later date at no charge. The airline, which has the most flights at Heathrow, canceled all short-haul flights today and said it was reviewing its long-haul schedule.
Megan Specia
Willie Walsh, director general of the International Air Transport Association, a global trade association of airlines, criticized Heathrow Airport, saying in a statement that the fire and power outage raised serious questions:“Firstly, how is it that critical infrastructure — of national and global importance — is totally dependent on a single power source without an alternative. If that is the case — as it seems — then it is a clear planning failure by the airport.”
Claire Moses
Reporting from London
The overnight blaze that knocked out power at Heathrow Airport also affected tens of thousands of other customers, including many homes, and forced the evacuation of dozens of residents because of smoky conditions.
But as the sun rose on Friday, power had been restored for most residents.
National Grid, the company that operates major systems that transport power from generation plants to consumption hubs in England and Wales, said it had restored power to 62,000 customers as of 6 a.m. local time.
The fire at its North Hyde substation, one of the facilities that provides power to Heathrow Airport, was brought under control a short time later, around 6:30 a.m.
Just before 11 a.m., a spokeswoman for National Grid said in an email that about 4,900 customers remained without power, but added that the utility was working to restore service.
The North Hyde facility receives high voltage power and converts it into lower voltage current, which is distributed through the local network to smaller substations; from there, it flows to homes and businesses.
The local power distribution network is owned by Scottish and Southern Electricity Networks, a utility based in Scotland.
North Hyde is one of multiple points that feed Heathrow Airport, supplying the area northeast of the airport, according to a recent planning document.
The cause of the blaze remains unclear. Ed Miliband, Britain’s energy secretary, said in a radio interview that there was no reason to suspect foul play. But he added that there still was no “real understanding of what caused the fire.”
In an interview with the British broadcaster Sky News on Friday, Mr. Miliband said that the blaze had affected a number of back up generators, further complicating the response.
Stanley Reed contributed reporting.
Megan Specia
The Metropolitan Police in London said in a statement that its counterterrorism specialists were leading the investigation into the substation fire and resulting power outage, “given the location of the substation and the impact this incident has had on critical national infrastructure.” The police said that “while there is currently no indication of foul play we retain an open mind at this time.”
Lynsey Chutel
Some travelers were able to check in at hotels around Heathrow, but rooms were filling up fast. Calvin Kim flew in from France on Thursday and stayed at the Hilton Garden Inn ahead of a flight to the U.S. When he found out the flight was canceled, he tried to stay another night, but the hotel was booked. “I got here last night, woke up and found out I’m not going home today,” he said. Kim reserved a room at another hotel and set off to find it. He said he hoped to return to Seattle tomorrow, “but who knows?”
Stephen Castle
In a statement, Prime Minister Keir Starmer said he was “receiving regular updates” about the situation at Heathrow and was “in close contact with partners on the ground.” He added that he knew the outage was “causing distress and disruption, especially for those traveling or without power in their homes,” and thanked the emergency services.
Ceylan Yeğinsu
At least 1,300 flights in and out of London’s Heathrow Airport were disrupted on Friday as the airport, Europe’s busiest, was shut down after a major nearby fire caused a power outage.
More flights are expected to be canceled or delayed in the coming days as airlines navigate the ripple effects of the airport’s closure, which is affecting air travel worldwide. About 220,000 passengers had been expected to travel through Heathrow on Friday, according to Flightrader24, the live flight tracking service.
Heathrow said it had no choice but to keep the airport closed until 11.59 p.m. on Friday. “We know this will be disappointing for passengers, and we want to reassure that we are working as hard as possible to resolve the situation,” an airport spokesman said in a statement.
If your travel has been affected by the closure, here’s what you need to know.
Passengers scheduled to travel in and out of Heathrow have been advised not to go to the airport, and to contact their airline for further information.
On Friday, the police turned away passengers trying to reach Heathrow, and cars in the area were diverted.
Most major airlines have updated information on their websites with details about flight disruptions and instructions for rescheduling canceled flights. You can also check their social media channels for updates.
If your flight departs from an airport in Britain, arrives there on a British or European Union airline, or arrives in an E.U. airport on a British airline, you are covered by British law.
Airlines are legally required to provide care and assistance for delays of more than two hours for short-haul flights, more than three hours for medium-haul flights and more than four hours for long-haul flights. You can check how the law applies to your flight here.
Under the regulations, airlines must provide a reasonable amount of food and drink, a means of communication, accommodations for passengers delayed until the next day, and transportation to and from the accommodations or a passenger’s home.
“The airline must provide you with these items until it is able to fly you to your destination, no matter how long the delay lasts or what has caused it,” the U.K Civil Aviation Authority says on its website.
Sometimes during major disruptions like the Heathrow Airport closure, airlines find themselves understaffed, overwhelmed and unable to keep up with passenger demand.
In such cases, the U.K. Civil Aviation Authority advises passengers to pay out of pocket and keep receipts to apply for reimbursement, and to ensure that costs are reasonable. Luxury hotels and alcohol will not be covered by airlines.
More detailed guidelines on how to claim costs or submit a complaint if a reimbursement request is rejected can be found here.
Usually, airlines are required to offer a refund or alternative routing if a flight is canceled, but only if the cancellation is the airline’s fault.
“Disruptions caused by things like extreme weather, airport or air traffic control employee strikes or other ‘extraordinary circumstances’ are not eligible for compensation,” according to the U.K Civil Aviation Authority.
Call your airline to see what options it has. British Airways, which has the most flights out of Heathrow, said it contacted its customers to offer flexible rebooking options — including with other airlines — or a full refund.
The airline is also offering all customers who booked to travel to or from Heathrow March 22 and 23 the option to rebook for free, a British Airways representative said.
Two carriers based in the United States also issued guidance for passengers stranded by the disruptions at Heathrow. Delta Air Lines said it would waive fare differences for flights rebooked on or before March 26. The airline advised passengers unable to reschedule flights within the guidelines to cancel and apply for credit at the value of the ticket, which can be used within one year of the ticket’s issue date. American Airlines said it would also waive change fees.
Comprehensive travel insurance policies usually cover flight delays and cancellations, so if you have coverage, be sure to read the conditions carefully.
The New York Times
Heathrow would typically be bustling on a Friday morning, but activity inside and outside of the airport has ground to a halt. The runways are empty, and the check-in desks are quiet.
Lauren Leatherby
Kennedy Airport in New York had the most flights scheduled to arrive at Heathrow today. Some of the more than 20 flights that were supposed to arrive from J.F.K. were diverted to Manchester, Glasgow or Reykjavik, Iceland. Others that were in the air at the time of the closure returned to New York.
Megan Specia
An official with the London Fire Brigade said in a briefing that the organization would be investigating the cause of the fire at an electrical substation that led to the power outage, alongside London’s Metropolitan Police.
The blaze involved “a transformer comprising 25,000 liters of cooling oil that was fully alight,” and about 10 percent of the original fire there was still burning, according to Jonathan Smith, the brigade’s deputy commissioner. He said there was still no power at Terminal 2 or Terminal 4 at Heathrow, but added, “I am pleased to report no one has been injured.”
Michael D. Shear
The fire at an electrical substation that crippled Heathrow Airport also took out at least one of the main backup systems designed to keep the power running, Britain’s energy secretary said, contributing to the lengthy disruption at Europe’s busiest air travel hub.
“There was a backup generator, but that was also affected by the fire, which gives a sense of how unusual, unprecedented it was,” Ed Miliband, Britain’s energy secretary, said in an interview early on Friday with Sky TV.
Mr. Miliband said the National Grid, which operates the transformer that failed near the airport, was trying to route power through a second backup system, but even that was proving difficult given the scale of the fire at the substation.
Transformers convert current from high voltage to a lower voltage. In the case of the transformer that caught fire, experts said it would have been turning 275,000 volts into 66,000 volts when it apparently failed. Jonathan Smith, the deputy commissioner for the London Fire Brigade, said the blaze involved “a transformer comprising 25,000 liters of cooling oil that was fully alight” at the substation.
By early afternoon on Friday, officials at National Grid said the network of the North Hyde substation, where the fire happened, had been reconfigured to restore power.
“This is an interim solution while we carry out further work at North Hyde to return the substation and our network to normal operation,” the power company said.
The failure of at least one backup system to quickly restore power after such a major outage is likely to be at the center of questions about the reliability of Britain’s infrastructure in the aftermath of the fire and airport closure. Those questions started within hours of the shutdown. In a post on social media, Willie Walsh, the director general of the International Air Transport Association, a global trade association of airlines, wrote: “How is it that critical infrastructure — of national and global importance — is totally dependent on a single power source without an alternative.”
“If that is the case — as it seems,” he added, “then it is a clear planning failure by the airport.”
Mr. Miliband said the government would focus on understanding the cause of the outage, telling Sky TV: “Obviously, with any incident like this, you will want to understand why it happened and what if any lessons it has for our infrastructure.”
Officials with National Grid did not immediately respond to an email requesting information about the backup systems.
In a statement, Heathrow Airport said the facility had “multiple sources of energy” but that there was no backup that would supply enough power to operate the entire airport, which it said “uses as much energy as a small city.” The statement said that backup diesel generators and uninterruptible power supplies did kick in that would have allowed planes to land and passengers to disembark. But they would not have been enough to allow the airport to operate fully.
Simon Gallagher, a former senior executive at Britain’s largest power provider, said that he believed the substation near Heathrow was designed so that if the first transformer has a problem, a second one could kick in quickly. But he said the fire appeared to have raged through the prevention systems and damaged both of the transformers.
That is highly unusual, he said, indicating a series of failures to the fire suppression systems that are designed to rapidly cut power to a faulty transformer to avoid that kind of damaging blaze.
“Basically, we designed things so that something can fail,” said Mr. Gallagher, who is now the managing director at U.K. Networks Services, which advises clients on the resilience of their electricity networks. But, he added, a number of things must have gone wrong “to allow that to fail, and then it’s damaged the one next to it as well.”
The police have said that counterterrorism investigators would examine the possibility of sabotage. But Mr. Gallagher said that judging by the video footage from the scene, the incident appeared to him to be a “classic transformer fault,” which happens often with little impact to customers because power is quickly routed to a nearby transformer.
The incident has raised questions about whether the airport had — or should have had — backup generators run by batteries or gas that might have allowed the entire airport to continue operating normally after the fire.
Mr. Gallagher said that was not possible given Heathrow’s current systems, which are not capable of providing enough energy to keep all of the lights on if the airport’s regular connection to the electrical grid is disrupted.
The emergency generator systems mentioned in the Heathrow statement were designed to keep runway lights and control tower systems working, he said, even during an incident like the one that took place on Friday.
But he said that it would have been impossible to continue to land planes because there would have been no electricity to move luggage, light the terminals, operate doors and more. To do that would require at least 20 massive diesel generators the size of a 40-foot shipping container, each one capable of generating a megawatt of power.
Heathrow did not have such a system, which would have been capable of keeping the power to the entire airport flowing for about six hours before needing to be refueled, he said. But he added that other major power customers, such as data centers, had installed big backup generators to ensure power in the event of an emergency.
“I think things will change,” Mr. Gallagher said. “I think Heathrow and other airports will install backup generation.”
A decision to do that could run up against questions about the impact on the environment. Officials at Heathrow have been working for years toward a “net zero” goal by increasing the efficiency of the planes that land at the airport and reducing the emissions of the infrastructure and cars on the ground.
Mr. Gallagher said that, contrary to some claims circulating on social media, none of those efforts would have caused Friday’s disruption, or prevented a quicker return of the power.
Megan Specia
Sadiq Khan, London’s mayor, released a statement thanking emergency responders for working overnight to tackle the fire that caused the outage at Heathrow. He said electricity suppliers were “working hard to restore power.”
“I know this will be hugely frustrating for the many thousands expecting to travel to and from Heathrow today, the families who have had their power cut and commuters who have had their journeys disrupted,” Khan added.
Nader Ibrahim
Aerial video captures an eerie stillness at Heathrow Airport, normally one of the world’s busiest, as planes remain grounded.
Lynsey Chutel
The Heathrow Express, a direct train line between the airport and Paddington Station, is ferrying airport and airline staff, along with a few redirected passengers, away from the airport. I was able to hop on at no charge. Usually a ticket costs around 25 pounds ($32). According to the line’s website, no passengers are allowed to board at Paddington.
Eshe Nelson
As Heathrow Airport, Britain’s busiest travel hub, shut down on Friday because of a nearby fire and power outage, airlines told thousands of travelers not travel to the airport and to check online for updates.
About 80 airlines operate at Heathrow, and they were diverting inbound flights to others airports in Britain, elsewhere in Europe or sending them back to their origin, while scrambling to rebook journeys.
“This will clearly have a significant impact on our operation and our customers,” British Airways said in a statement. The airline was the most affected as it had about 340 flights scheduled to land at Heathrow on Friday, according to data from Flightradar24.
The airline had redirected all flights already on their way to Heathrow on Friday morning to other airports in Britain.
Virgin Atlantic, another British airline, said it had canceled all flights until 9:30 p.m. London time, “with the rest of today’s schedule currently under review,” it said in a statement.
The airline was asking customers to not travel to Heathrow or their scheduled departure airport if Heathrow was their destination and not to contact customer services. Instead, they said travelers should check their flight status on the airline’s website and people with canceled flights would be emailed rebooking details.
Air France had canceled eight return flights from Paris-Charles de Gaulle Airport to Heathrow on Friday, but flights to other airports in Britain were operating as normal, the airline said.
KLM, a Dutch airline, said it had canceled three return flights from Amsterdam to London Heathrow and would rebook passengers. But the airline said that it would try to accommodate passengers with an “urgent need” to fly to London by placing them on flights to an airport near London.
Lufthansa, a German airline, said all customers on flights in and out of Heathrow have been rebooked, but it urged customers to keep their contact details updated.
Nine flights by Qatar Airways between Heathrow and Hamad International Airport near Doha, were affected. For example, one flight was redirected to Frankfurt and another to Brussels.
Air India had canceled most of its flights to Heathrow, though one returned to Mumbai and another was diverted to Frankfurt.
Qantas, an Australian airline, said its Singapore to London and Perth to London services were diverted to Paris on Friday, with buses arranged to take customers to London. Flights departing from Sydney and Perth on Friday and expected to land in London on Saturday morning where still scheduled to run as normal.
On their websites, most airlines say canceled flights are rebooked free of charge. Costs are likely to mount for airlines as they redirect flights and compensate customers for hotel rooms, food, transportation and other costs related to upended schedules.
Shares in airline companies dropped in European trading. Though the losses were easing by midmorning, shares in IAG, the parent company of British Airways, Aer Lingus, Iberia and two other airlines, were down about 1 percent. Air France-KLM shares dropped about 1.6 percent.
Ryanair, an Irish airline, said it had added eight “rescue” flights to its schedule for Friday and Saturday between Dublin and London Stansted airports.
Lauren Leatherby, Melissa Eddy and Liz Alderman contributed to reporting.
