Firefighters got the call at about 11.23 p.m. on Thursday, 20 March 2025. A transformer inside the North Hyde electrical substation in Hayes, west London, was burning. By Friday morning one of the busiest airports on earth had stopped.
The substation sits around 6.5 kilometers from Heathrow, and the blaze took out the power feeding it. Ten fire engines and about 70 firefighters worked through the night. Some 150 people were evacuated from nearby properties and a 200-meter cordon went up as a precaution. Thousands of homes lost electricity; Scottish and Southern Electricity Networks later put the figure at more than 63,000.
Heathrow, which handles more than 80 million passengers a year, announced it would stay shut until 11.59 p.m. on Friday. “Passengers are advised not to travel to the airport,” it said. The tracking service FlightRadar24 counted at least 1,350 flights to and from Heathrow affected. Qantas sent its Perth-London and Singapore-London services into Charles de Gaulle and arranged buses onward to the British capital. United Airlines said its Friday departures would land at Heathrow on Saturday morning instead.
A single point of failure
The question that dominated the day was how a hub of that size could go dark from one fire. Energy Secretary Ed Miliband called the blaze “catastrophic” and said it had also knocked out the airport’s backup generator. Willie Walsh, who runs the airline trade body IATA, was blunter. “How is it that critical infrastructure — of national and global importance — is totally dependent on a single power source without an alternative,” he wrote on X, calling it a “clear planning failure by the airport”.
The picture turned out to be more complicated. Heathrow’s three substations each have a back-up, and the fire disabled both the damaged site and its reserve. Emergency diesel generators and batteries did work, but they only run safety essentials such as landing equipment and runway lights. National Grid’s chief executive, John Pettigrew, told the Financial Times that two other substations stayed up and either could have supplied the airport. Heathrow’s chief executive, Thomas Woldbye, said the problem was not a shortage of power but the time it took to move the load across.
That took hours because of what had to happen first. “It’s fuelling systems, it’s bridges, it’s escalators,” Woldbye told the BBC, describing the machinery that had to be shut down, restarted and tested before anyone could be let back in.
Cause and aftermath
Police said there was no indication of foul play, though counterterrorism detectives led the inquiry into the cause. The London Fire Brigade said its own investigation would concentrate on the electrical distribution equipment at the substation.
Flights began to resume after 18 hours, once National Grid had reconfigured its network around the substation and restored an interim supply. On Saturday, Heathrow said it was “open and fully operational”.
The prime minister, Keir Starmer, said there were “questions that need to be answered”. The government ordered a six-week investigation led by the National Energy System Operator, with initial findings expected in May.
Sources
- Heathrow Airport flights resume after fire cut power (DW)
- National Grid boss says Heathrow had 'enough power' after substation fire (BBC News)
- Heathrow Airport closed for 24 hours as fire sparks major power outage (7NEWS)
