Heathrow Airport in London was plunged into chaos after a fire at an electrical substation shut down operations at one of Europe’s busiest air hubs, forcing the airport to cancel or divert more than 1,000 flights on Friday and removing a global linchpin of air travel.

Heathrow’s chief executive, Thomas Woldbye, described the disruption as “unprecedented,” telling reporters on Friday that the airport had lost power equal to that of a midsize city, and that though a backup transformer worked as it should, there had not been enough power for the entire airport.

Some flights resumed late Friday. But Mr. Woldbye said, “We expect to be back in full operation, so 100 percent operation as a normal day” by Saturday.

The Metropolitan Police in London said later on Friday, “After initial assessment, we are not treating this incident as suspicious, although inquiries do remain ongoing.” The police said counterterrorism officials would lead the investigation into the cause of the blaze, which broke out Thursday night at an electrical substation northeast of Heathrow.

It was too early on Friday to calculate the precise cost of the outage. But the disruption raised questions about the resilience of Britain’s largest airport and why it appeared to be so reliant on a single electrical substation.

Residents of the Hayes neighborhood near the airport described hearing two loud bangs and seeing “a massive ball of flame” shoot into the sky on Thursday night. Minutes later, the airport said it was shutting down all air traffic, incoming flights were diverted, and passengers at Heathrow were sent home. Nearby residents were also evacuated.

By Friday morning, roads around the power station were cordoned off, and a helicopter hovered above. An odd stillness had descended on Heathrow. The runways were empty, the check-in desks quiet, digital flight information screens were blank, and passageways were dimly lit by emergency lighting. It was a lifeless calm not seen even during the early panicked weeks of the coronavirus pandemic.

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 substation held 25,000 liters of cooling oil, which fueled the large blaze and made it too difficult to extinguish, the London Fire Brigade said on Friday. The brigade said about 5 percent of the fire was still burning by Friday evening.

The airport closure resulted in dozens of flights from the United States landing far from their original destination. They were diverted to airports in Glasgow, Madrid and even Happy Valley-Goose Bay, a tiny town in the Canadian province of Newfoundland and Labrador.

John Connor, 22, sat at Newark Liberty International Airport in New Jersey 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.”

Frantic travelers swarmed social media to ask airlines about managing canceled flights and upcoming departures, claiming in posts on X that airline apps were lagging in notifying passengers about cancellations and that customer service could not be reached by phone.

Some travelers stuck in Europe were urged to consider traveling by rail. After finding out that his flight from Heathrow was canceled, Phillip Kizun, 58, of Chester County, Pa., had to improvise as he tried to get from London to Dublin for a work trip. He took a train to Wales and then a ferry from the coastal town of Holyhead to the Irish capital. He met several European and American travelers doing the same.

“It was an absolute real ‘Planes, Trains and Automobiles,’” Mr. Kizun said, minutes after arriving in Dublin, referring to the 1987 Steve Martin-John Candy comedy.

Some planes already in the air had to turn around. Jeannie LaChance, who was traveling to London from Los Angeles with her sister and 2-year-old niece, said that about four hours into the flight, the pilot announced they would have to return.

“Everyone was pretty calm, which I think was nice because we’re all trapped in a plane,” Ms. LaChance, 31, said.

Some airlines said they would issue waivers allowing free rebookings, including British Airways, Delta Air Lines, American Airlines and United Airlines. A Delta spokesperson said the airline would reimburse the cost of traveling to London by train for passengers who had their flights diverted to Amsterdam.

Cirium, an aviation data company, estimated that as many as 290,000 passengers could be affected by Heathrow’s closure.

By late Friday, several flights had landed at or departed from Heathrow, as the airport began to rumble back to life, about 16 hours after the fire. The first to touch down there was a British Airways plane that had traveled from Gatwick Airport in London after being diverted from its original destination, Singapore, according to the flight-tracking service FlightAware.

A Heathrow spokeswoman said the airport was working to first restore “repatriation flights and relocating aircraft.”

Britain’s Department of Transport said it was temporarily lifting restrictions on overnight flights to ease congestion.

But the chief executive of British Airways, Sean Doyle, warned that Heathrow’s closure would have “a huge impact” on the airline’s customers over the coming days. British Airways had been set to operate more than 670 flights carrying about 107,000 customers on Friday, and similar numbers were planned over the weekend, he added.

“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.

The Heathrow crisis was likely to upset not only the movement of people, but also the flow of goods. The closure of the crucial aviation hub, even for a short time, would cause delays and logistical headaches for many businesses that ship products through Heathrow, supply chain experts said.

Heathrow has two runways and four terminals that serve more than 230 destinations in 90 countries. Last year, about 83.9 million passengers and 1.7 million tons of cargo traversed the airport. It is the third-largest hub for air cargo in Western Europe, measured in metric tons shipped. Goods worth nearly 200 billion pounds ($258 billion) went through Heathrow in 2023, about a fifth of the value of the British goods trade.

“Goods move around the globe in a really precise, timed way on a daily basis,” said Ben Farrell, chief executive of the Chartered Institute of Procurement and Supply, a global network of supply chain professionals based in London. “Any disruptions to any part of that leads to a knock-on effect elsewhere.”

British businesses will likely be most affected. Global trade can be handled by other large airports in Europe, said Eytan Buchman, chief marketing officer at Freightos, a digital shipping marketplace.

Mr. Woldbye, Heathrow’s chief executive, apologized to travelers for the shutdown and said the airport had done well to resume flights by Friday evening, given the scale of the outage.

The airport closure came 15 years after one of Europe’s most severe air travel disruptions, when a volcano eruption in Iceland sent ash miles into the sky and obstructed travel for millions, including at Heathrow.

The ash grounded more than 100,000 flights over nearly a week in April 2010 as it drifted across Northern Europe. The airline industry’s losses from the volcanic disruption were estimated at $1.7 billion.

Reporting was contributed by Christine Chun, Michael Levenson, Michael D. Shear, Peter Eavis, Christopher Maag, Ivan Penn, Stephen Castle, Niraj Chokshi, Ceylan Yeğinsu, Claire Moses, John Yoon and Qasim Nauman

If it wasn’t obvious that Prime Minister Benjamin Netanyahu of Israel believes he has an ally in his battle against the country’s attorney general, its judges and even the head of its domestic security service, he made it clear on Wednesday evening.

“In America and in Israel, when a strong right wing leader wins an election, the leftist Deep State weaponizes the justice system to thwart the people’s will,” he wrote in a social media post. “They won’t win in either place! We stand strong together.”

The defiant, Trumpian blast was the latest evidence that Mr. Netanyahu and President Trump are running the same playbook to achieve strikingly similar goals: to neuter the judiciary, dismantle a system of oversight that puts a check on their authority and discredit national security professionals they see as arrayed against them.

These moves come as Mr. Trump has aligned his Middle East policy squarely to benefit Mr. Netanyahu, including giving the Israeli prime minister freedom to renew the war in Gaza and launching U.S. airstrikes against the Houthis in Yemen, a group that is an avowed enemy of Israel.

In just this week in Washington, Mr. Trump called for the impeachment of a federal judge who was seeking basic information about his mass deportation efforts, fired two Democratic commissioners of an independent trade commission and was rebuked by a judge who said his administration’s gutting of the agency in charge of foreign aid most likely violated the Constitution.

This week in Jerusalem, Mr. Netanyahu’s cabinet fired Ronen Bar, the head of Shin Bet, Israel’s equivalent of the F.B.I., after the agency started investigations into the prime minister’s aides. Among other claims, the aides are accused of mishandling classified information and leaking a document to a foreign newspaper. Mr. Netanyahu’s office has strongly denied the allegations.

Mr. Netanyahu’s move against the Shin Bet chief came weeks after his administration announced plans to fire the attorney general, Gali Baharav-Miara, an apolitical judicial official appointed by the previous government who has frustrated Mr. Netanyahu by blocking some of his decisions on legal grounds.

Like Mr. Trump, Mr. Netanyahu is seeking to rein in domestic watchdogs and judicial authorities that, like in the United States, have pursued investigations against him or his allies.

Like Mr. Trump, the Israeli prime minister has faced criminal charges that he says are false claims fomented by left-leaning and unelected bureaucrats. In Mr. Netanyahu’s case, he is standing trial in a yearslong corruption case that requires him to appear in court several times a month.

“Trump’s own illiberalism has given Netanyahu an unprecedented opportunity to impose his own on Israel,” said Aaron David Miller, a Middle East expert at the Carnegie Endowment for International Peace. “Trump’s popularity in Israel and the Vulcan mind meld between Trump and Netanyahu on undermining the independence of the courts, and fighting the ‘woke left’ protects and energizes Netanyahu.”

Mr. Miller said Mr. Netanyahu had long taken cues from other authoritarian leaders, like Prime Minister Viktor Orban of Hungary. And Mr. Netanyahu’s battle against what he calls the “deep state” predates Mr. Trump’s presidency.

He was first questioned by the police about the corruption charges in early 2017, weeks before Mr. Trump took office for his first term. When Mr. Netanyahu’s trial began in 2020, he stood on the steps of the court in Jerusalem, accusing the prosecution, the police and the media establishment of a joint attempt “to thwart the will of the people.” He is accused of granting regulatory favors to businessmen and media moguls in exchange for gifts and favorable news coverage, which he denies.

The prime minister’s formal attempts to undermine judicial power began in 2022, when his coalition government introduced legislation intended to limit the power of the Supreme Court and give the government more control over the appointment of its judges. After mass protests, the government suspended most of these moves for more than a year.

But Mr. Netanyahu appears galvanized after Mr. Trump’s election in November. Since then, his government revived the overhaul of the judicial appointments process and is pushing the bill through Parliament.

One Israeli official briefed on Mr. Netanyahu’s thinking said that Mr. Trump’s election had given the prime minister greater confidence to take provocative steps at home and in the war in Gaza, which escalated this week after the collapse of a cease-fire deal that had been brokered earlier this year. The official spoke on the condition of anonymity.

For his part, Mr. Trump has found common cause with other illiberal leaders like Mr. Orban, Prime Minister Narendra Modi of India and President Vladimir V. Putin of Russia. Mr. Trump said this month that Mr. Putin “went through a hell of a lot with me,” referring to the F.B.I’s investigation into Russian interference in the 2016 election and contacts between the Trump campaign and Russian operatives.

It was in the midst of that investigation when Mr. Trump fired James B. Comey, the F.B.I director who had refused to publicly clear him of any ties to Russia. Mr. Comey had also refused to give in to Mr. Trump’s pressure to drop an F.B.I. investigation into Michael T. Flynn, the former White House national security adviser.

Eight years later, Mr. Netanyahu persuaded his cabinet to fire Mr. Bar, despite large street protests in Jerusalem this week denouncing his threats to remove the Shin Bet chief. On Friday, Israel’s Supreme Court issued an injunction freezing Mr. Bar’s dismissal until the justices could hear petitions that had been filed against it.

Alon Pinkas, a political commentator and Israel’s former consul-general in New York, said it was doubtful Mr. Netanyahu would have moved against the Shin Bet chief had Mr. Trump not been president. The two leaders were kindred spirits politically, he said, and had “both adopted an identical language that would make George Orwell cringe with envy.”

Mr. Trump and Mr. Netanyahu also regularly use this language to discredit the news media, another institution they often view with contempt. Israel’s national broadcaster, Kan, reported this week that it was during a meeting with Mr. Trump in Washington last month when Mr. Netanyahu was inspired to fire Mr. Bar.

Asked to comment on that report, Mr. Netanyahu’s spokesman, Omer Dostri, responded with a terse text message: “fake news.”

Phillip Kizun found himself having to improvise on Friday as he tried to get from London to Dublin, typically a routine trip.

After finding out that his flight from Heathrow Airport had been canceled, Mr. Kizun, 58, took a train to Wales and then a ferry from the coastal town of Holyhead to the Irish capital. He met several European and American travelers who were doing the same.

“It was an absolute real ‘Planes, Trains and Automobiles,’” Mr. Kizun said, minutes after arriving in Dublin for a work trip, referring to the 1987 Steve Martin-John Candy comedy.

Mr. Kizun, 58, of Chester County, Pa., was among the thousands of anguished travelers who found themselves stranded on Friday, after a fire at an energy substation near Heathrow caused a power outage that closed the airport for the better part of a day. Some Heathrow-bound flights turned around in midair, while many others did not take off, leaving confused and anxious passengers wondering when they might finally get where they were going.

The New York Times asked readers to share their stories. Some, like Mr. Kizun, found alternative routes. Others remained in a state of limbo. A few simply gave up.

Planes were turned around midflight.

Some planes that were already in the air turned around. That was the case for the one carrying Jeannie LaChance, who was traveling to London from Los Angeles with her sister and 2-year-old niece. About four hours into the flight, the pilot let the passengers know that there was a possible fire at Heathrow and that they would have to return.

“Everyone was pretty calm, which I think was nice because we’re all trapped in a plane,” Ms. LaChance, 31, said.

Henry Kofman, 20, a sophomore at the University of Southern California, chose London as a spring break because of its theater scene. He was having such a good time that he decided to extend his trip by a day.

Tough luck. He was up late watching the “Severance” season finale when he got a news alert on his phone that Heathrow had been shut down. It seemed unreal.

“I just don’t find it believable that the busiest airport in Europe is just gone for the day,” he said.

Mr. Kofman is hoping that operations return to normal on Saturday, as airport officials have promised, so he can be back in Los Angeles in time for classes to resume on Monday.

Some travelers changed their itineraries.

Cyndi Darlington, a marketing executive, was set to take her best friend on her first overseas trip, to London and Rome. The pair sat on the plane for three hours at the San Diego airport. When they were told that the flight had been canceled, Ms. Darlington and her friend moved swiftly to reorganize their trip. Now they will head straight to Rome, cutting two days off their vacation.

“We overheard people on the plane talking about going to a wedding and making connections,” Ms. Darlington said. “And so we feel that we’re kind of lucky. And we only lost two days.”

The outage forced some passengers to cancel their trips entirely. Iris Planamento was on a plane at Newark Liberty International Airport on Thursday night, waiting to take off for a package tour that would take her to London, Normandy and Paris. After her flight was canceled, she visited an online chat forum for the tour, where people were sharing stories about being turned back midair or otherwise being diverted or delayed. Not wanting to deal with the stress, Ms. Planamento, 72, canceled her trip.

“I have to tell you that I am not a person who has anxiety problems,” she said. “For the past few weeks, I’ve been feeling a lot of anxiety. I’ve never felt that before, and yesterday was especially bad until I got to the airport and had a few drinks. Today I’m fine. I feel I’m disappointed. But the anxiety is gone.”

Camille Dee, 74, of Roslyn, N.Y., and her husband were supposed to take off from Kennedy International Airport for London on Friday night for what she described as their first vacation in six years. Their flight was canceled, and the earliest rescheduled flight that the airline is offering her is on Monday. Worried that the new itinerary may cost her hundreds of dollars in nonrefundable hotel fees and other associated costs, she is considering canceling the trip, though she did allow that her travails amounted to a “first-world problem.”

“After this, it’s going to be a while before I decide to go back to London, because this whole thing has left such a bad taste in my mouth,” Ms. Dee said.

‘A little unnerving’: The closure fueled anxiety.

Alyse Franklin, 22, a senior at Indiana University, was stressed out, not knowing when she would be able to make it home from a spring break trip with 19 classmates from her international marketing and communications class.

“Flying in general kind of makes me feel a little ill,” Ms. Franklin said. “So it’s not fun to fly already, but the fact that we don’t know when it’s going to happen and it feels like I can’t mentally prepare for it, it’s a little unnerving.”

Andrew Tate and his brother, Tristan Tate, the online influencers who decamped last month to the United States while facing human-trafficking charges in two European countries, were set to return on Friday to Romania ahead of a criminal proceeding, one of them said Friday.

The British American siblings were expected to arrive at night in Bucharest, Romania’s capital, a representative for them told The New York Times.

The pair, who have millions of followers on social media and are known for their misogynistic views and for flaunting their wealth, arrived in Florida on Feb. 27 after a Romanian court lifted travel restrictions against them.

“Spending 185,000 dollars on a private jet across the Atlantic to sign one single piece of paper in Romania,” Andrew Tate wrote Friday on X. “Innocent men don’t run. THEY CLEAR THEIR NAME IN COURT.”

The Tates’ visit to the United States was polarizing and spawned speculation about whether President Trump, with whom the brothers have openly aligned themselves, had used his influence to allow them to travel. But Mr. Trump said he knew nothing about it. Marcel Ciolacu, the prime minister of Romania, said on social media last month that the United States had not made any requests in connection with the influencers.

The brothers received a chilly reception from two top Florida officials, with Gov. Ron DeSantis saying that they were not welcome there and the state’s attorney general, James Uthmeier, also a Republican, opening a criminal investigation into them.

It was not clear how long the Tates were planning to stay in Romania, where they were arrested in 2022 on accusations of luring women to the country and sexually exploiting them.

Joseph McBride, their lawyer in the United States, did not immediately respond to a request for comment on Friday.

According to Romanian prosecutors, the brothers misled several women into believing that they wanted a relationship with them. The women were instead housed in a compound near Bucharest and forced to appear in online pornographic videos, prosecutors said.

But a Bucharest court set back the case in December, when it found that it did not meet the requirements for a trial. Prosecutors vowed that they would continue to pursue the charges.

While the criminal proceedings have been playing out in Romania, the British authorities have pursued the Tates’ arrest on charges of rape and human trafficking. A group of women suing Andrew Tate there over claims of sexual assault has pressed the British government to have him and his brother extradited from Romania.

And an American woman filed a lawsuit against the brothers last month in Florida, accusing them of luring her to Romania, conspiring to coerce her into sex work and defaming her after she gave testimony to the Romanian authorities.

Benjamin Bull, a lawyer for the woman who is the plaintiff in the civil case and the general counsel for the National Center on Sexual Exploitation, said in a statement on Friday that the lawsuit was proceeding.

“The Florida court still has jurisdiction over them no matter where they are physically located, so we are not concerned that they are going back to Romania,” he said.

The arrival of the Tate brothers in the United States divided conservatives, including those in the media. The brothers, who have not responded to requests for an interview, have appeared on podcasts that support Mr. Trump and were welcomed by Dana White, the chief executive of the Ultimate Fighting Championship and an ally of the president.

The president’s eldest son, Donald Trump Jr., has also sided with the brothers in the past, calling the jailing and house arrest of Andrew Tate “absolute insanity” in a May 2023 social media post.

Not all conservatives have sympathized with the brothers, who have been criticized by the commentators Megyn Kelly and Ben Shapiro.

It was not clear whether the Tates’ departure from the United States might play a role in the preliminary criminal inquiry that Mr. Uthmeier, Florida’s attorney general, opened earlier this month.

His office did not immediately respond to a request for comment on Friday. Nor did a spokesman for Mr. DeSantis.

While the brothers were staying in Florida, Andrew Tate confronted Mr. DeSantis over his recent comments that they were not welcome there and that the state was looking into whether it had jurisdiction in the matter.

“I dare you to arrest me and charge me so I can clear my name in a court of law,” Mr. Tate wrote on X. The brothers even met with the rapper Ye, formerly known as Kanye West, during their time in the United States, according to their lawyer.

“I AGREE WITH EVERYTHING ANDREW TATE HAS EVER SAID,” the rapper said on X this month.