Jonathan Josephs
Business reporter

Image source, Getty

Airlines are adjusting their schedules to help passengers reach their destinations after Heathrow’s closure.

One approach is something they call "regauging" – swapping smaller planes for bigger ones where possible.

For example, instead of using an A320 for flights from Istanbul to London Gatwick, Turkish Airlines is using A330s, which can carry more passengers.

Other airlines are making similar moves.

One challenge they might face is whether airports can handle the extra passengers.

More travellers mean more suitcases, which means more baggage handlers are needed to process the extra load.

How have flights been affected?published at 16:40 Greenwich Mean Time 21 March

16:40 GMT 21 March

By Rob England, Wesley Stephenson and Krystina Shveda

More than 1,300 flights have been disrupted by the closure of Heathrow Airport today, according to the air traffic website flightradar24.com.

As of 14:30, it says:

• 1,149 flights have been cancelled
• 119 have been diverted
• 35 are still showing as “scheduled”
• 14 are still being given estimated arrival times
• 1 is showing as delayed

For those diverted, Amsterdam and Gatwick airports are the most common destinations so far.

Just under half of the flights affected belong to British Airways, according to the data.

Virgin Atlantic is the next most affected, with 68 flights, followed by Lufthansa.

The website says the live figures are gathered using multiple sources and are subject to change throughout the day.

We've just received a fuller statement from Heathrow Airport, which says it can restart some flights later today and hopes to be fully operational tomorrow:

"Our teams have worked tirelessly since the incident to ensure a speedy recovery. We're pleased to say we're now safely able to begin some flights later today.

"Our first flights will be repatriation flights and relocating aircraft. Please do not travel to the airport unless your airline has advised you to do so.

"We will now work with the airlines on repatriating the passengers who were diverted to other airports in Europe. We hope to run a full operation tomorrow and will provide further information shortly.

"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."

We can bring you more now from the latest update from Heathrow Airport.

It says it hopes to "run a full operation tomorrow and will provide further information shortly", having just announced it is now safely able to "restart" flights.

It says its teams have worked "tirelessly since the incident to ensure a speedy recovery".

It also urges passengers not to travel to the airport unless the airline has advised them to do so.

Heathrow Airport says it's now "safely able to restart flights".

In a statement shared on X, it says it will prioritise "repatriation and relocation of aircraft".

We'll bring you more from its update shortly.

Image source, Getty Images

British Airways has announced a short while ago it has cancelled all its short-haul flights to and from Heathrow today.

Now most of its long-haul flights have also been cancelled, according to chairman and CEO Sean Doyle.

"We hope that power will be restored as soon as possible. But even when that does happen, this incident will have a substantial impact on our airline and customers for many days to come, with disruption to journeys expected over the coming days," he says.

Doyle adds that unexpected diversions mean some planes and crew are now in locations they weren’t meant to be. And because crew can only work a set number of hours, the airline faces the challenge of getting new teams to operate those flights, he says.

Ruth Cadbury, who chairs the Transport Select Committee, says there are questions about Heathrow Airport's resilience that need answering.

Cadbury, who represents Brentford near Heathrow, hopes we'll learn more about the cause of the fire later today.

She tells BBC News: “The concern is it was dependent on one substation for its power, and that does raise questions about infrastructure resilience.”

She also wonders if grid capacity played a role.

“Here in west London, we do have an issue about the overall grid capacity challenge in the boroughs of Hounslow, Hillingdon and Ealing, because the data centres are huge users of electricity but I think it is a question for Heathrow Airport, about whether they had previously considered this resilience concern themselves.”

She says the select committee will, in time, hold a session with key figures to examine what happened.

Rich Preston
News correspondent

We've been hearing the phrase "Critical National Infrastructure" a lot.

So what is it?

The UK's National Protective Security Authority (NPSA) defines it as "facilities, systems, sites, information, people, networks and processes, necessary for a country to function and upon which daily life depends".

The NPSA is the government agency responsible for reducing the vulnerability of national infrastructure. It's part of the Security Service, better known as MI5.

The UK's national security strategy, known as the Integrated Review, highlights the need to keep these sites running smoothly and safely.

Usually, we think about that in terms of preventing terror attacks or cyber threats. But today’s chaos has been caused by a single fire at one power station.

Whether that was deliberate or not, we don’t yet know. But there are serious questions about why better resilience wasn’t in place to protect such a vital part of British infrastructure.

Image source, Getty Images

Here's the latest as disruption continues for passengers travelling to and from Europe's busiest airport:

What we know

• Power appears to have returned to Terminal 4 at Heathrow, according to PA news agency
• National Grid says an "interim solution" has been found to restore power, allowing affected customers to be reconnected
• Despite this, the airport will stay closed until at least 23:59 GMT today

What we don't know

• When Heathrow will reopen
• How much of a knock-on effect the disruption will have on flights after today
• What exactly caused the fire – counter-terrorism officers are investigating, but the Met Police says there's currently no sign of foul play

British Airways says it has cancelled all short-haul flights to and from Heathrow today.

"Our teams are currently working hard to review our long-haul schedule," the airline says, as well as looking into the implications "for our schedule for tomorrow and beyond".

Travel journalist Simon Calder says even if power is restored, tomorrow will still be "far from a normal day" for the airport.

Ongoing issues could mean disruption "stretch into next week", he says.

"Ultimately it's extremely damaging to the UK economically, reputationally and so much distress to people," he says. "All those people have been let down."

James Kelly
BBC News

Image source, Maz Cooper

Psychology student Maz Cooper, 18, from Hampshire, was meant to go on a college trip to Poland today.

She says it's ridiculous that a substation fire could shut down such a large airport.

"It was a psychology trip to go to Auschwitz as its main aim," Maz says.

"We came to college this morning completely unsure if we'd be going, waiting until 12 when our teachers unfortunately broke the news that we couldn't go.

"I want to emphasise the stress and panic the teachers organising this had to go through due to the lack of resilience from Heathrow Airport, let alone the students who were left in limbo until it was confirmed the trip was cancelled.

"I understand this is a complicated situation, but the fact that there's no back-up plan for problems like this is, frankly, ridiculous."

It's been more than 14 hours since the fire started, and there's still smoke coming from the substation.

Image source, Reuters

Image source, Reuters

Image source, Reuters

The National Grid says it has found "an interim solution" to restore power to customers, including Heathrow Airport.

In its latest update, it says it has reconfigured the network from North Hyde substation, allowing all affected customers to be reconnected. This includes the ability to resupply parts of Heathrow Airport linked to the substation.

The National Grid stresses that this is only a temporary fix.

An update from PA news agency reporters at Heathrow.

They say power seems to be back on at Terminal 4.

The lights are on in the main building, and the lifts in the multi-storey car park are working again, they add.

Your Voice, Your BBC News
James Kelly

Image source, EPA

Jake Baines from Portsmouth was meant to meet a woman he’d befriended online for the first time today.

But her flight from Chicago was cancelled, turning their plans for a "fun-filled week" into a "total nightmare".

Jake only found out about the cancellation while travelling by coach to London.

He’s now in a Premier Inn near the airport, where he says the power is out.

All is not lost, though. He tells the BBC his pen pal's trip has just been delayed until the weekend.

"It will still be memorable... albeit for the wrong reasons!"

Asya Robins
Live reporter

Harbans Kaur Johal, 81, was flying back to Heathrow after visiting her brother in India when her flight was diverted to Munich Airport this morning.

She speaks no German and very little English and was "a bit panicked and flustered", and had wandered around the airport alone for some time, unsure where to go, her son Ajai Johal says.

Ajai says he was "really angry" at British Airways for losing her, calling the situation "outrageous".

He and his wife Jas made several phone calls to British Airways staff and passengers on the same flight who were trying to help.

Thanks to "kind-hearted" people who offered her a place to stay, Harbans is now at a hotel near the airport, waiting to find out when she can travel.

Ajai and Jas think airlines should assume some passengers don’t speak English and have policies to support them in situations like this.

Ben King
Business reporter

Heathrow has strong resilience and response plans and is well prepared, says a consultant who has worked on airport resilience in the UK.

When the airport identifies possible vulnerabilities, the consultant, speaking anonymously to protect working relationships, says it spends a lot of money to fix them.

"I would not assume that there is a technical deficiency in the plans at Heathrow," he says.

But with a system as complex as a modern airport, he says it's impossible to prevent incidents altogether.

Image source, PA Media

Eurostar says it is adding more seats on its trains between London and Paris to help airline passengers affected by Heathrow's closure.

It will run two extra services in each direction on Friday, with space for around 882 passengers per train.

Passengers are advised to check the website or app for booking details, Eurostar says.

Your Voice, Your BBC News
Thomas Copeland

Image source, BBC/Adam Boggon

Adam Boggon from Culross is heading back to Scotland for a friend’s wedding after trip to the US.

He’s been waiting at Boston Logan Airport since early this morning, hoping to find out when he can fly home.

He says about half a dozen British Airways staff are there, trying to reroute passengers.

“A man from British Airways has set me up with something through New York tonight which might get me to Loch Lomond in time for the reception.

"Will have to see how it goes," he says.