A fire at an electrical substation supplying London Heathrow Airport caused a major power outage, leading to the grounding of thousands of flights and the evacuation of 180 people. Authorities are investigating the cause, while airlines like British Airways work to rebook stranded passengers amid widespread travel disruption. The UK's busiest airport is shut today, and thousands of flights are grounded after a fire broke out at the electrical substation that supplies the airport. London Heathrow was without power on Friday, March 21, after the blaze broke out overnight in Hayes, west London. London Fire Brigade confirmed that 10 engines and approximately 70 firefighters were sent to the scene, and no one was injured. Approximately 180 people have been evacuated from their homes with a 200 meter cordon put in place around the substation. Homes and businesses have been left without power, including Heathrow Airport, which has had to ground thousands of flights. Heathrow Airport said in a statement: "Due to a fire at an electrical substation supplying the airport, Heathrow is experiencing a significant power outage. To maintain the safety of our passengers and colleagues, Heathrow will be closed until 23h59 on 21 March. "Passengers are advised not to travel to the airport and should contact their airline for further information. We apologize for the inconvenience." Thousands of flights were due to depart from and arrive at Heathrow today. These include flights from across Europe and locations such as Chicago, Washington D.C., New York, and Toronto. The main airline based out of Heathrow is British Airways (BA) at Terminal 3, which partners with American Airlines for transatlantic flights. BA said in a statement: "Due to a power outage in the London Heathrow area, London Heathrow Airport is currently closed. As a result, customers due to travel from Heathrow on Friday are advised not to travel to the airport until further notice. "This will clearly have a significant impact on our operation and our customers and we're working as quickly as possible to update them on their travel options for the next 24 hours and beyond." Firefighters douses flames of a fire that broke out at a substation supplying power to Heathrow Airport in Hayes, west London on March 21, 2025. Britain's Heathrow airport, Europe's busiest, was shut down early on March 21 for 24 hours after a major fire at an electricity substation cut power to the sprawling facility west of London, officials said. (Photo by BENJAMIN CREMEL / AFP) (Photo by BENJAMIN CREMEL/AFP via Getty Images) The UK’s second busiest airport, Gatwick, said it would accept some flights from Heathrow, posting on X: “We are aware of the situation at Heathrow Airport today and are supporting as required. Flights from London Gatwick are operating as normal today." What caused the fire? Passengers stranded due to the blaze are pushing for questions as to how such a massive site—a little under five square miles—was left entirely without power. The nation's energy secretary, Ed Miliband, told Sky News that the fire also damaged the airport's backup generator. The politician added that the damage to both the main and backup generators is indicative of how "unusual and unprecedented" the situation is. He added it was "too early to know" what caused the substation blaze, but said he was in contact with the National Grid—England and Wales's electricity distribution service—to provide updates. "There is a third backup—a second backup if you like—which they are seeking to use to restore power. There are backup mechanisms in place but given the scale of this fire backup mechanisms also seem to have been affected," he continued. "Obviously with any incident like this we will want to understand why it happened and what, if any lessons, it has for our infrastructure." LONDON, ENGLAND - MARCH 21: Departure boards and other screens are dark as Heathrow airport experienced a significant power outage in the early hours of March 21, 2025 in London, England. A fire at the North Hyde electricity substation in Hayes has caused a power outage at Heathrow Airport, leading to all flights in and out to be cancelled until midnight tonight, affecting around 200,000 passengers. Some homes near to the fire have also been evacuated. (Photo by Klara Simonova/Getty Images) London Fire Brigade added its fire investigators are working closely with the Metropolitan Police Service on the investigation into the cause of the fire.  "As the morning progresses, disruption is expected to continue, and we urge people to avoid the area whenever possible," added the Brigade's assistant commissioner, Pat Goulbourne. Aviation expert, John Strickland, added to BBC show 5Live that systems will be in place to ensure passenger safety at the extremes of emergency situations. However, because of the scale of airport services, disruption to power supply has wide-ranging consequences: "There are just so many systems at an airport used by so many different players, not only the airport itself and the airlines, but handling agents, engineering companies, catering companies, you name it." While this could include something as minor as lights in toilets, it also includes extra services like baggage being loaded and aircraft maneuvering around the airport. Customer reaction Customers are being asked by BA to directly message them on social media platforms like X—formerly known as Twitter—in order to rebook their flights. The airline is also directing passengers to its flight status page to keep them updated on when services will resume. One customer in the Maldives told Sky that delayed passengers had been given meal vouchers to apologize for the inconvenience, saying: "Absolutely no news given, because assumedly there is no news to give.  "We were given 'meal' vouchers almost as soon as we got through security, which we thought was kind.  We then went to get this meal only to be told it's only worth £14 so doesn't even cover the cost of a meal in this airport.  "The notice board says nothing more than delayed." Stranded passengers makes their way down unlit stairs due to lifts not working to the car park at Heathrow Terminal 4 in London. More than 1,300 flights to and from Heathrow Airport will be disrupted on Friday due to the closure of the airport following a fire at the North Hyde electrical substation last night. Picture date: Friday March 21, 2025. (Photo by James Manning/PA Images via Getty Images) Tori Dunzello was en-route to Heathrow from Newark Airport in the U.S. when she noticed her plane had done a 'U-turn' in the air. Speaking to the BBC, Dunzello said: "I saw the time on the screen started to increase so I turned on my world map and I started seeing a big U-turn ... I called the assistant over and said 'Are we turning around?' And she said 'Yes we are because of a massive fire in Heathrow.'" The plane subsequently stopped to refuel in Canada. According to tracking website FlightRadar24, more than 100 planes bound for Heathrow were in the air when the closure was announced. This story was originally featured on Fortune.com ...read more read less