Thousands of passengers are facing delays and cancellations after a massive fire ripped through an electricity substation near Heathrow Airport.

Up to 300,000 customers were set to fly through Europe’s biggest airport on Friday, with around 1,351 flights affected by the mysterious blaze.

Ten fire engines rushed to Nestles Avenue, Hayes, a suburban street around five miles north of the airport, where 70 firefighters tackled the inferno throughout the night from 12am, London Fire Brigade said.

Follow live updates here

Scottish and Southern Electricity Networks said London Heathrow and 16,300 homes in Hayes and Hounslow were hit by a widespread power cut due to the fire.

Around 150 residents were evacuated from nearby properties and a 200-metre cordon was put in place around the substation, police said. It is unclear what caused the fire.

Here, The Independent takes a look at all we know about the fire about how it has affected flights going in and out of Heathrow Airport.

What caused the fire?

The London Fire Brigade said it was investigating the cause of the blaze, which is currently unknown and was reported around midnight.

Footage showed the fire ripping through a Scottish and Southern Electricity Networks-managed substation throughout the night, as dozens of firefighters rushed to extinguish it.

Energy minister Ed Miliband told LBC Radio there was no suggestion that there was foul play.

He also told BBC: “It’s obviously an unprecedented event, but we will want to understand both the causes of this event and what lessons, if any, it can teach us.”

What is the economic impact?

Air transport consultant John Strickland said Heathrow’s closure will cost the aviation industry millions of pounds.

“It will run into millions. You can’t quantify it yet. Heathrow has normally about 200,000 passengers a day, so it’s a massive impact in lost revenues and disruption costs,” he said.

British Airways owner International Consolidated Airlines Group (IAG)’s share price had plunged four per cent – equivalent to losing more than half a billion pounds in market capitalisation by 8.30am GMT.

How many passengers have been affected?

London Heathrow said it would be closed until midnight on Friday to “maintain the safety of our passengers and colleagues”.

Up to 291,000 passengers were set to fly from Heathrow Airport on Friday, with 1,330 flights scheduled throughout the day, according to aviation analytics firm Cirium.

Up to 665 departures were scheduled, equating to over 145,094 seats, and 669 flights were due to arrive, equating to 145,836 seats.

According to flight tracking website FlightRadar24, Australian carrier Qantas Airways sent its flight from Perth to Paris, and a United Airlines New York flight was instead heading to Shannon, Ireland.

EasyJet said it was putting larger aircraft on key routes today and over the weekend to provide additional seats to help customers affected by the Heathrow closure travel today.

Ryanair has also put on extra flights from Dublin to London Stansted “to rescue passengers affected by today’s Heathrow closure”.

When will Heathrow reopen?

Passengers have been asked not to travel to the airport “under any circumstances”, while British Airways said it would not be operating flights out of its global hub “until further notice”.

It is unclear when the airport will reopen. A spokesperson said: “Due to a fire at an electrical substation supplying the airport, Heathrow is experiencing a significant power outage.

“To maintain the safety of our passengers and colleagues, Heathrow Airport will be closed until midnight on 21 March.

“Passengers are advised not to travel to the airport and should contact their airline for further information. We apologise for the inconvenience.”