Heathrow Airport will reopen for a limited number of flights today, after a large fire at a nearby electrical substation disrupted travel for around 200,000 passengers.
Counter-terror police are among the agencies investigating the cause of the blaze, which triggered a "significant power outage" that led to more than 1,000 flights to and from the airport being cancelled.
National Grid said an "interim solution" had been found to restore supplies to customers including Heathrow Airport.
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Proximity of Heathrow to the electrical substation
Image: The proximity of Heathrow to the electrical substation
Just after 4pm, a Heathrow spokesperson said the airport was "safely able to begin some flights later today".
The first flights will be repatriation flights and relocating aircraft, with Heathrow working with airlines to bring back the passengers diverted to other airports across Europe.
"We hope to run a full operation tomorrow and will provide further information shortly," the spokesperson added.
"Our priority remains the safety of our passengers and those working at the airport. As the busiest airport in Europe, Heathrow uses as much energy as a small city, therefore getting back to a full and safe operation takes time. We apologise for the inconvenience caused by this incident."
British Airways says eight long-haul flights will depart from 7pm, with the airline "urgently contacting customers" to tell them to come to the airport.
The only customers who should make their way to Heathrow Airport are those booked onto the following flights: BA055 to Johannesburg, BA057 to Johannesburg, BA011 to Singapore, BA259 to Riyadh, BA045 to Cape Town, BA059 to Cape Town, BA015 to Sydney via Singapore, and BA249 to Buenos Aires via Rio de Janeiro.
'Significant disruption in the coming days'
Earlier, the airport said it expected "significant disruption over the coming days" and warned passengers "not travel to the airport under any circumstances until the airport reopens". All trains to Heathrow were suspended.
Some power has returned to Terminal 4, with lights in the main building and lifts in the multi-storey car park operational again.
Police direct traffic outside Terminal 5 at the Heathrow International Airport.
Pic: Reuters
Image: Police directing traffic away from Heathrow's Terminal 5. Pic: Reuters
Airplanes remain parked on the tarmac at Heathrow International Airport.
Pic: Reuters
Image: It is estimated up to 1,357 flights could be affected on Friday. Pic: Reuters
The disruption began late on Thursday night when fire crews were called to a blaze in west London at an electricity substation serving Heathrow and local properties.
Flightradar24 estimated 1,357 flights would be affected today. Around 120 flights were in the air bound for Heathrow when the airport announced it would be closing for the day. Some were turned around while others were diverted to other airports in the UK and Europe.
Pic: Flightradar24
Flightradar screengrab from post on X showing flights early on Friday morning heading to heathrow.
https://x.com/flightradar24/status/1902928403189096822/photo/1
Image: Flightradar24 showed up to 120 planes in the air would be forced to divert or turn back. Pic: Flightradar24/X
Heathrow is one of the world's busiest airports and had a record 83.9 million passengers last year, with a plane landing or taking off around every 45 seconds.
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Fire at substation in Hayes is extinguished while Heathrow's runways remain deserted 0:53
Runways deserted as substation fire is put out
Fire was 'something out of a movie'
The North Hyde substation fire has been described as "absolutely apocalyptic" by a driver who witnessed it last night.
"Billowing black smoke" covered Heathrow and lights went out along the roads in the Hounslow and Southall area, Adeel Anwar told Sky News.
"The sky was darkening and it was just a scene that was chaotic. It looked like something out of a movie."
He said he felt the heat of the fire as he passed the substation with his window open.
Photo taken with permission from the social media site X, formerly Twitter, posted by @JoselynEMuirhe1 of the fire at Hayes electrical substation. More than 1,300 flights to and from Heathrow Airport will be disrupted on Friday due to the closure of the airport following the fire. Issue date: Friday March 21, 2025.
Image: The height of the fire was described as 'absolutely apocalyptic'. @JoselynEMuirhe1/X/PA
Firefighters extinguish the fire at the North Hyde electrical substation, which caught fire Thursday night and lead to a closure of Heathrow Airport in London, Friday, March 21, 2025.(AP Photo/Kirsty Wigglesworth)
Image: Pic: AP
Thousands of passengers stranded
Some 83,857,000 passengers were recorded at Heathrow's terminals in 2024, according to data from the Civil Aviation Authority. That's the equivalent of about 229,000 passengers using the hub every day.
Aviation analytics firm Cirium told the New York Times that it believes as many as 290,000 passengers could be affected today - enough to fill Wembley Stadium three times.
The airport's total closure is set to have knock-on effects on airline operations around the world for several days to come.
Passengers are stuck in "no man's land", according to travel expert Simon Calder. But he told Sky News airlines are "absolutely responsible" for providing a hotel, giving you meals and getting you to your destination if you're flying on a British or European airline out of Heathrow.
Flight delayed or cancelled? What are your rights?
Stranded passengers at Heathrow Terminal 5.
Pic: PA
Image: Stranded passengers at Heathrow Terminal 5. Pic: PA
Stranded passengers at Heathrow Terminal 5 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.
Image: Pic: PA
British Airways, the biggest carrier at Heathrow, said it is offering passengers travelling to or from Heathrow between Friday and Sunday the option to rebook their flights to a later date for free through their website.
Virgin Atlantic also said the airport's closure "has had a significant impact on our flying programme", adding that the rest of Friday's schedule was under review. It advised passengers to check their website for updates.
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Heathrow Airport is deserted after fire at substation cuts power 0:40
'It's all dark here, mate': Fire cuts Heathrow power
Gatwick Airport said in a statement that it is "supporting by accepting diverted flights as required" and that it is operating "as normal today".
National Infrastructure Commission Chair Sir John Armitt said the incident highlights a need for infrastructure operators to be fully prepared for dealing with short term shocks, particularly for failures outside their control.
"That means building resilience into all their systems, regularly stress testing, and increasing cooperation with other operators to identify risks arising from increasing interdependence," he said.
"We've been clear the UK needs national resilience standards for our transport, digital, energy and water infrastructure."
Extra services being laid on
Ryanair has launched what it is calling eight "rescue flights" on Friday and Saturday between London Stansted and Dublin. Eurostar is also adding two extra services - one each way - between London and Paris.
And easyJet is using larger-than-planned aircraft on key routes on Friday and over the weekend between the UK and Milan, Amsterdam, Edinburgh, Paris, Munich and Madrid.
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Counter-terror officers investigating
The Metropolitan Police has declared a major incident and has confirmed their Counter Terrorism Command is now leading inquiries to examine the cause of the fire.
"While there is currently no indication of foul play we retain an open mind at this time," the Met said in a statement.
It added that counter-terror officers were involved because of their "specialist resources and capabilities" to progress the investigation "at pace to minimise disruption and identify the cause".
London mayor Sir Sadiq Khan said the presence of counter-terrorism police should not alarm people and is not unusual.
Heathrow shutdown: What we know so far
Oil fire still alight at substation
The fire that caused the power outage is at the North Hyde substation in Hayes, about 1.5 miles to the north of the airport.
London Fire Brigade's (LFB) deputy commissioner Jonathan Smith told reporters at a news conference the fire involved a transformer - a key part of the substation - with 25,000 litres of cooling oil "fully alight".
The North Hyde electrical substation which caught fire last night. More than 1,300 flights to and from Heathrow Airport will be disrupted on Friday due to the closure of the airport following the fire. Picture date: Friday March 21, 2025.
Image: Smoke was continuing to rise above the North Hyde electrical substation this afternoon. Pic: PA
Smoke rises from a fire at the North Hyde Electricity Substation.
Image: Pools of what looks like foam surround the damaged substation. Pic: PA
Crews evacuated 29 people from neighbouring properties but there were no casualties.
In all, 67,000 households were left without power after the fire at the substation, but all supplies have been restored.
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Alice Delahunty, president of electricity transmission at the UK's National Grid, told Sky News they were working to supply Heathrow with power through alternative routes.
She also said she did not recognise reports linking discarded smoking materials with the cause of the fire.
A spokesperson for National Grid said their work to restore power was "an interim solution" and they were carrying out further work "to return the substation and our network to normal operation".
Firefighters at the North Hyde electrical substation which caught fire. More than 1,300 flights to and from Heathrow Airport will be disrupted on Friday due to the closure of the airport following the fire. Picture date: Friday March 21, 2025. PA Photo. See PA story FIRE Hayes. Photo credit should read: Jonathan Brady/PA Wire
Image: Fire crews said the blaze was now under control. Pic: PA
Smoke rises from a fire at electricity substation.
Image: Aerial footage shows the scale of the damage the fire has done to the substation
Earlier LFB said 10 engines and around 70 firefighters had been working to extinguish the blaze - with the first 999 call received at 11.23pm on Thursday.
Pictures from the scene showed large flames and plumes of thick black smoke.
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Heathrow denies 'planning failure'
The International Air Transport Association (IATA), the trade body for airlines, has been highly critical of what it believes to be "a clear planning failure by the airport".
Director general Willie Walsh, former chief executive of British Airways, said the closure of Heathrow "will inconvenience a huge number of travellers".
"How is it that critical infrastructure, of national and global importance, is totally dependent on a single power source without an alternative? If that is the case, as it seems, then it is a clear planning failure by the airport," he said.
Heathrow insisted the airport's "back-up diesel generators and uninterruptable power supplies" did work "as expected" but "are not designed to allow us to run a full operation".
Heathrow Airport in numbers:
• 83,857,000 passengers used Heathrow's terminals in 2024, according to data from the Civil Aviation Authority
• 78.8 million international passengers used Heathrow in 2024 (28.1 million travelled within the EU and 50.7 million to non-EU countries). The remaining 5 million was domestic traffic.
• The equivalent of around 229,000 passengers a day use the hub, although the figure varies during the year due to demand
• Around 1,317 aircraft a day use Heathrow, compared to about 726 a day at Gatwick
• Heathrow handled a total of 482,143 aircraft last year (479,506 passenger and 2,637 cargo), Civil Aviation Authority data shows
• Annual passenger numbers at Heathrow dwarf those of Gatwick (43,242,000), Manchester (30,756,000) and Stansted (29,694,000)
In a statement the airport said it uses as much energy as a small city and "back-up systems are safety systems which allow us to land aircraft and evacuate passengers safely".
Separately Mr Walsh also demanded that there should be "a fairer allocation of passenger care costs than airlines alone picking up the tab when infrastructure fails".
"Until that happens, Heathrow has very little incentive to improve," he argued.
Travel consultant Paul Charles told Sky News he believed the cost to Heathrow and airlines is already in the millions and is likely to rise.
On the assumption flights resume within 48 hours, he estimated costs would be between £20m and £30m.