Warren Hu had just settled into his flight from New York to London, where he planned to visit his girlfriend, when he became one of the thousands of passengers whose travel was thrown into disarray early Friday because of a fire near Heathrow Airport.
The plane carrying Mr. Hu, a college student in New York, would be returning to the United States, a crew member announced. “I’m a bit surprised, but we can find a solution, so I’m trying to stay calm,” he said in a text message from the plane.
The fire, at an electrical substation near Heathrow, knocked out power at the airport, one of the world’s busiest, forcing the authorities to close it for all of Friday. They warned that flight disruptions could last for days.
A glance at Heathrow’s flight information board on Friday morning gave a sense of just how big the shock waves from the closure would be. Flights from Vietnam, Brunei and India were scheduled to land Friday morning. Passengers were expecting to board planes taking them to dozens of destinations: Tokyo and Singapore, Minneapolis and Miami.
In the Chinese city of Shenzhen, Lukas Zou was among the travelers waiting for news about their now-delayed flight to London. Mr. Zou, who works at a trading firm, said he learned of the Heathrow shutdown just as he was about to board his Shenzhen Airlines flight, scheduled to depart at 1:45 p.m. local time.
“With so much luggage, I don’t know if I should laugh or cry. I’ve already booked a hotel room in London, and it can’t be canceled,” Mr. Zou said. He said that Shenzhen Airlines was arranging hotel rooms for the affected passengers, and that their flight might now be rescheduled for 2 a.m.
Dozens of airlines fly to Heathrow from about 180 places worldwide. Many planes already in the air were forced to divert to other airports.
As many as 290,000 passengers traveling in or out of Heathrow could be affected by the closure, according to Cirium, an aviation analytics company. On Friday, 669 flights were scheduled to take off from Heathrow, Cirium said.
Heathrow is the main hub for British Airways, which said it was redirecting flights already on their way to Heathrow to other airports in Britain, where possible.
At Fiumicino airport in Rome, dozens stood in line at the British Airways counter, hoping to learn about their flights. The airport’s information board showed that four British Airways flights were canceled on Friday morning.
A group of high school students from Arizona, planning to fly home via Heathrow after a week in Italy, arrived at Fiumicino to disappointment. “We didn’t find out the flight was canceled until half of our party had checked in,” said Angel Brady, a chaperone on the trip. She said the group would miss its connecting flight to Phoenix.
North American, Asian and Australian airlines were also affected. American Airlines, Delta Air Lines, United Airlines, Air Canada and JetBlue were among those having to divert their Heathrow-bound jets or return them to the airports they had come from.
Singapore Airlines said that a flight that left for Heathrow at 9 a.m. local time on Friday was returning to Singapore, and that five flights to London on Friday had been canceled.
Australia’s Qantas diverted two Heathrow-bound flights to Paris.
Nicholas Yong contributed reporting from Singapore.
