Heathrow Airport is to remain shut until midnight due to a large fire at a nearby electricity substation.
A spokesperson said there was a “significant power outage across the airport” and “we do not have clarity on when power may be reliably restored”.
Passengers have been warned to stay away.
Follow live updates on Heathrow closure
“To maintain the safety of our passengers and colleagues, we have no choice but to close Heathrow until 23h59 on 21 March 2025,” the statement added.
“We expect significant disruption over the coming days and passengers should not travel to the airport under any circumstances until the airport reopens.”
Tracking site Flightradar24 estimates at least 1,351 flights in and out of Heathrow will be affected today, including around 120 already in the air this morning.
Flights usually begin around 5am after the regular overnight quiet period.
Some planes have already been diverted to places including Gatwick, Paris, and Shannon in Ireland.
London 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.
Its total closure is set to have knock-on effects on airline operations around the world.
British Airways, the biggest carrier at Heathrow, reiterated that customers should not go to the airport until further notice.
A statement 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.”
The fire that caused the power outage is at a substation in Hayes, about 1.5 miles to the north of the airport, and an estimated 16,000 homes nearby are also without electricity.
Pictures from the scene – on Nestles Avenue – show large flames and plumes of thick black smoke.
Around 150 people have been evacuated and a 200-metre cordon is in place.
London Fire Brigade (LFB) said 10 engines and around 70 firefighters were working to extinguish the blaze – with the first 999 call received at 11.23pm.
It said a transformer within the North Hyde substation was alight but the cause is so far unknown.
A National Grid spokesperson said they “working at speed to restore power supplies as quickly as possible” after the fire damaged equipment.
Heathrow is one of the world’s busiest airports. File pic: PA
LFB Assistant Commissioner Pat Goulbourne said it would be “a prolonged incident”.
“As we head into the morning, disruption is expected to increase, and we urge people to avoid the area wherever possible,” he said.
Scottish and Southern Electricity Networks said shortly after midnight that a “widespread power cut” was affecting Hayes, Hounslow and surrounding areas.
However, it estimated it would be “resolved by 3am”.
A graphic on the company’s website suggested around 16,000 homes were affected.
Firefighters from Heathrow, Hayes, Hillingdon, Southall and other stations are all involved in the response.
Police are supporting the firefighters, while residents have been urged to keep windows and doors closed due to the smoke.
