A large fire near London's Heathrow Airport knocked out power Friday to Europes busiest flight hub, forcing it to shut down all day and disrupting global travel for hundreds of thousands of passengers.At least 1,350 flights to a nd from Heathrow were affected, flight tracking service FlightRadar 24 said, and the impact was likely to last several days as passengers try to reschedule their travel and airlines work to get planes and crew to the right places.Authorities do not know what caused the fire but so far they have no evidence it was suspicious.Residents in west London described hearing a large explosion, followed by a fireball and clouds of smoke, when the blaze ripped through the electrical substation near the airport.Some 120 flights were in the air when the closure was announced, with some turned around and others diverted to Gatwick Airport outside London, Charles de Gaulle Airport near Paris or Irelands Shannon Airport, tracking services showed.Lawrence Hayes was three-quarters of the way to London from New York when Virgin Atlantic announced they were being diverted to Glasgow.It was a red-eye flight and Id already had a full day, so I dont even know how long Ive been up for, Hayes told the BBC as he was getting off the plane in Scotland. "Luckily I managed to get hold of my wife and shes kindly booked me a train ticket to get back to Euston, but its going to be an incredibly long day.Heathrow is one of the worlds busiest airports for international travel. It had its busiest January on record earlier this year, with more than 6.3 million passengers, up more than 5% from the same period last year.Still, the disruption Friday fell short of the one caused by the 2010 eruption of Icelands Eyjafjallajokull volcano, which spewed clouds of ash into the atmosphere and created trans-Atlantic air travel chaos for months.Fire under control but impact to last daysIt was too early to determine what sparked the huge blaze about 2 miles (3 kilometers) from the airport, but theres no suggestion of foul play, Energy Secretary Ed Miliband said.Still, the Metropolitan Police force said counterterrorism detectives are leading the investigation into the cause because of the location of the electrical substation fire and its impact on critical national infrastructure. The force said counterterrorism command has specialist resources and capabilities that can help find the cause quickly.They are working with the London Fire Brigade.Miliband said the fire, which took seven hours to control, also knocked out a backup power supply to the airport. Heathrow said in a statement that it had no choice but to close the airport for the day.We expect significant disruption over the coming days, and passengers should not travel to the airport under any circumstances until the airport reopens," the airport said.Heathrow was at the heart of a shorter disruption in 2023 when Britains air traffic control system was hit by a breakdown that slowed takeoffs and landings across the U.K. on one of the busiest travel days of the year.Anita Mendiratta, an aviation consultant, said the impact of the closure will be felt over two to four days as airlines, cargo carriers, and crews are moved into position and passengers rebooked.As soon as the airport opens up at midnight tonight, its not only about resuming with tomorrows flights, its the backlog and the implications that have taken place, Mendiratta said. Crew and aircraft, many are not where theyre supposed to be right now. So the recalculation of this is going to be intense.Diverted, canceled and in limboAt Heathrow, a family of five traveling to Dallas showed up in the hopes their flight home still listed as delayed would take off.But when Andrea Sri brought her brother, sister-in-law and their three children to the airport, they were told by police that there would be no flight.It was a waste of time. Very confusing, said Sri, who lives in London. We tried to get in touch with British Airways, but they dont open their telephone line until 8 a.m.Travelers who were diverted to other cities found themselves trying to book travel onward to London. Qantas airlines sent flights from Singapore and Perth, Australia, to Paris, where it said it would bus people to London, a process likely to also include a train shuttle beneath the English Channel.Budget airline Ryanair, which doesn't operate out of Heathrow, said it added eight rescue flights between Dublin and Stansted, another London airport, to transport stranded passengers Friday and Saturday.National Rail canceled all trains to and from the airport.Flights normally begin landing and taking off at Heathrow at 6 a.m. due to nighttime flying restrictions. But the skies were silent Friday morning.Living near Heathrow is noisy, there are planes every 90 seconds or so, plus the constant hum of traffic, but you get used to it, to the point of no longer noticing, said James Henderson, who has lived next to the airport for more than 20 years. Today is different, you can hear the birds singing.Blaze lit up the sky and darkened homesMatthew Muirhead was working Thursday night near Heathrow when he stepped outside with a colleague and noticed smoke rising from an electrical substation and heard sirens crying out.We saw a bright flash of white, and all the lights in town went out, he said.The London Fire Brigade sent 10 engines and around 70 firefighters to control the blaze and about 150 people were evacuated from their homes near the power station.This was a very visible and significant incident, and our firefighters worked tirelessly in challenging conditions to bring the fire under control as swiftly as possible, Assistant Commissioner Pat Goulbourne said.Scottish and Southern Electricity Networks said in a post on X the power outage affected more than 16,300 homes.The U.K. government earlier this year approved building a third runway at the airport to boost the economy and connectivity to the world. ...read more read less