Counter terror police are leading the investigation into the “unprecedented” electrical substation fire that has closed down London Heathrow, stopping more than 1,300 flights as engineers tried to restore power to the airport on Friday.
Airlines face days of disruption with hundreds of thousands of scheduled passengers already unable to fly in and out of Europe’s busiest airport, after what ministers said was an “unusual and unprecedented incident”.
London fire brigade was called shortly after 11pm on Thursday to a fire at an electrical substation in Hayes, west London, with power also cut to thousands of homes.
More than 70 firefighters tackled the blaze, which the brigade said at 8am was under control, with more than 20,000 litres of oil having caught fire in a transformer. Officers said that despite the acrid smell, there was no air quality danger to the public.
The cause of the fire is unknown, although security sources indicated there was no immediate indication of foul play.
A spokesperson for the Met Police said: “We are working with the London Fire Brigade to establish the cause of the fire which remains under investigation. While there is currently no indication of foul play we retain an open mind at this time.
“Given the location of the substation and the impact this incident has had on critical national infrastructure, the Met’s Counter Terrorism Command is now leading enquiries.
“This is due to the specialist resources and capabilities within that command that can assist in progressing this investigation at pace to minimise disruption and identify the cause.”
The detectives have the security clearance to access sensitive material as investigators try to establish the fire’s cause.
Heathrow is regarded a potential target for terrorism or sabotage, the incidence of which, backed by state actors, has been rising in recent years.
National Grid said substation fires were “extraordinarily rare” and it was not able to “rule anything in or out”.
More than 1,350 flights had been scheduled on Friday to and from Heathrow, Britain’s biggest airport and one of the busiest in the world. Power was still cut off to two of the airport’s four terminals, T2 and T4, by late morning.
The immediately cancelled or rerouted flights had capacity for up to 291,000 passengers, with a significant proportion connecting onwards, as well as carrying freight.
Airline operations around the world will be affected, with the knock-on effects expected to last several days.
According to the online flight tracking service FlightRadar24, 120 flights to Heathrow were in the air when the closure was announced. Some arriving flights from Asia and Australia were diverted to other airports around Britain and Europe while others coming from the US returned to their departure points.
A Heathrow spokesperson said: “To maintain the safety of our passengers and colleagues, we have no choice but to close Heathrow until 23h59 on 21 March 2025. We expect significant disruption over the coming days and passengers should not travel to the airport under any circumstances until the airport reopens.
“We know this will be disappointing for passengers and we want to reassure that we are working as hard as possible to resolve the situation.”
British Airways, which operates just over half of the flights from Heathrow, said: “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.”
Global airlines body Iata said it was “yet another case of Heathrow letting down both travellers and airlines”. Willie Walsh, Iata’s director general, added: “How is it that critical infrastructure is totally dependent on a single power source without an alternative? If that is the case then it is a clear planning failure by the airport.”
The UK’s biggest carriers based at other airports, easyJet and Ryanair, said that they would be adding extra capacity to help stranded passengers. EasyJet will fly bigger planes on some key European routes while Ryanair has added additional flights from Ireland to London Stansted.
National rail and coach services operating to Heathrow have all been cancelled today.
The UK energy secretary, Ed Miliband, said it was an “unusual and unprecedented incident”. He said the government would be doing everything it could to restore power to the airport, after supply lines were changed to restore electricity to most of the 67,000 homes affected on Friday morning.
Asked how a fire at a single substation had been able to severely disrupt the UK’s busiest airport, he said: “We don’t know the cause of this fire. It’s obviously an unprecedented event.”
Miliband said he understood that there was a backup system but that it had also been affected by the extent of the fire.
Alice Delahunty, the president of National Grid’s transmission business, said it had been “a very significant and serious incident, which is extraordinarily rare in our network,” and that it was not possible to verify any “rumours and speculation” over the cause of the fire.
She said: “We’re not in a position to rule anything in or out. Our focus has been getting homes and businesses back on supply safely. There will be a time for a full and thorough investigation, but the focus has been on restoring power.”
The fire damaged the substation’s primary transformer, while the backup transformer sustained heat damage during the blaze, Delahunty said.
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The London fire brigade assistant commissioner Pat Goulbourne said firefighters had worked “tirelessly in challenging conditions to bring the fire under control as swiftly as possible”.
Emergency services were called to the scene at 11.23pm on Thursday. The fire left forced more than 100 people to evacuate. Firefighters led 29 people from surrounding properties to safety, and reported no casualties.
While Heathrow has experienced significant disruption from external events such as the air traffic control outage in August 2023 and the mass groundings during the Covid crisis, the last time the airport was fully closed for an extended period was during heavy snowfall and freezing conditions in December 2010, when 4,000 flights were cancelled.
Heathrow is the best connected airport in the world, according to analysts OAG, serving around 230 destinations. A record 83.9 million passengers used it last year, and it claims to be the largest single-site employer in the UK, with around 90,000 people in total working at the airport.
Additional reporting by Jamie Grierson, Elias Visontay and Kate Lamb
