“Heathrow is experiencing a significant power outage,” the airport operator said in a statement on its website, adding it would be closed until just before midnight Friday (2359 GMT).
“Passengers should not travel to the airport under any circumstances until the airport reopens.”
Some 120 flights heading to Heathrow were in the air when the closure was announced, FlightRadar24 said.
London Fire Brigade said there had been a “significant” fire at a substation in Hayes, a nearby town in the London borough of Hillingdon, which caused the power outage.
It said 10 fire engines and around 70 firefighters were on the scene, while around 150 people had been evacuated from nearby properties.
Images on social media — which could not immediately be verified by AFP — showed huge flames and smoke rising from the substation.
Other videos, apparently shot inside Heathrow’s terminals, showed shuttered shops and deserted corridors, lit only by emergency lighting.
“The fire has caused a power outage affecting a large number of homes and local businesses, and we are working closely with our partners to minimise disruption,” said London Fire Brigade assistant commissioner Pat Goulbourne.
He said the blaze was first reported at 11:23 pm (2323 GMT).
“This is a highly visible and significant incident, and our firefighters are working tirelessly in challenging conditions to bring the fire under control as swiftly as possible,” a statement said.
British utility firm Scottish and Southern Electricity Networks said on its website that an “unplanned outage” had left more than 16,000 homes without power in the area.
Heathrow handles more than than 80 million passengers a year and the operator says there are around 1,300 takeoffs or landings a day.
Seven United Airlines flights returned to their airport of origin or to other airports and all Friday flights to London Heathrow are being cancelled, a spokesperson said.
British Airways said in a statement that the closure of its main hub “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 UK’s second busiest airport Gatwick said it would accept some flights from Heathrow.
“We are aware of the situation at HeathrowAirport today and are supporting as required. Flights from London Gatwick are operating as normal today,” it said on X.
In Sydney, Qantas said two flights en route to Heathrow -– a non-stop flight from Perth and another via Singapore — had both been diverted to Paris’s Charles de Gaulle airport.
In January, the government gave permission for Heathrow to build a third runway — which could be ready by 2035 — after years of legal wrangling brought on by complaints from local residents.
Five major airports serve the British capital and towns nearby.
But capacity is stretched, especially at Heathrow whose two runways each measure almost four kilometres in length, while the airport covers a total area 12.3 square kilometres.
It opened in 1946 as London Airport before being renamed Heath Row, a hamlet demolished two years earlier to make way for the construction.
Situated 25 kilometres (15 miles) west of central London, Heathrow currently has four terminals and serves 200 destinations in more than 80 countries.
Among its main flight destinations last year were Dublin, Los Angeles, Madrid and New York. – AFP
