Matt Spivey
Live editor

Image source, Reuters

The day began with passengers flooding into Heathrow as the airport confirmed it was fully operational after a complete shutdown on Friday - caused by a power outage sparked by a fire at a nearby substation.

Despite the resumption of planes landing and taking off, disruption is still ongoing with more than 100 flights having been cancelled or delayed on Saturday.

We heard from some of those affected including Liz, who was "devastated" to miss her youngest son's graduation in Sterling and friends Farah and Niken who have missed part of their friend's wedding in Cambodia.

In a gripping interview on BBC Radio 4's Today programme, Heathrow chief Thomas Woldbye said he was "proud" of how the airport handled the incident.

This afternoon, the government ordered an "urgent investigation" into the power outage, as Energy Secretary Ed Miliband said he is "determined" to understand "what happened and what lessons need to be learned".

We then heard again from Woldbye who said he is committed to a thorough investigation and hopes the findings will "strengthen the airport's future resilience".

We'll soon be closing our live coverage, but it remains unclear how much longer disruption will affect flights at Heathrow. Thanks for joining us.

• Investigation ordered into power outage that closed Heathrow
• Heathrow boss 'proud' of response to power outage chaos
• How did a single fire bring down Europe's busiest airport?

As we've been reporting, the government has ordered the National Energy System Operator (NESO) to conduct an investigation into the power outage at Heathrow Airport.

Let's recap what the key players have been saying:

Energy Secretary Ed Miliband says he will work in partnership with Ofgem to "properly understand what happened and what lessons need to be learned".

Transport Secretary Heidi Alexandersays it is "imperative" to "identify how this power failure happened and learn from this to ensure a vital piece of national infrastructure remains strong".

Akshay Kaul, director general for infrastructure at Ofgem, says the regulatory authority will "not hesitate to take action", adding that they will work to ensure NESO's review "goes as far as possible" to ensure steps are put in place to avoid similar events in the future.

Fintan Slye, Chief Executive of NESO - who have been commissioned to lead the investigation -welcomed the commission adding that the operator will work with "all relevant stakeholders to understand the lessons that can be learned to improve the future resilience of Britain’s energy system".

Heathrow Airport's Chief Executive Officer Thomas Woldbye welcomed the investigation and hopes the findings will "help strengthen the airport's future resilience".

Heathrow's backup power supplies - how they operatepublished at 17:31 Greenwich Mean Time 22 March

17:31 GMT 22 March

published at 17:31 22 March

17:31 22 March

Tom Symonds
BBC correspondent

Heathrow has three electricity substations known as "Grid Supply Points", each with a backup. There are also reserve diesel generators.

• What is a substation?

Uninterruptible battery-powered supplies provide enough power to keep safety critical systems - such as aircraft landing systems - running. These supplies do not have enough power to keep the whole airport in operation.

Heathrow also has a biomass-fuelled combined heating and power station, producing 10 megawatts of power, which feeds electricity and heat to Terminal Two.

The fire at North Hyde Point in Hayes put both the substation, and its backup, out of action. On Friday, Heathrow's main fall-back was the two remaining grid supply points.

The airport's chief executive, Thomas Woldbye, said these remaining grid supply points were capable of powering Heathrow, but only after a complex process.

This involved reallocating the remaining supplies then restarting and testing everything from escalators to aircraft fuelling systems - which took most of Friday to achieve.

Image source, EPA-EFE/REX/Shutterstock

The independent National Energy System Operator (NESO), which will investigate the power outage, says it "welcomes the government's commission".

Fintan Slye, NESO's chief executive, says in a statement: "We will now work with all relevant stakeholders to understand the lessons that can be learned to improve future resilience of Great Britain’s energy system."

The Department Energy Security and Net Zero says it expects NESO to report back with initial findings within six weeks.

NESO is expected to work with Heathrow Airport to ensure the investigation is "comprehensive and thoroughly examines the causes of the incident," the statement adds.

Heathrow Airport's Chief Executive Officer Thomas Woldbye welcomes the investigation into the power outage that closed Heathrow Airport on Friday.

In a statement issued in the last few minutes, he says he hopes the findings will "help strengthen the airport's future resilience".

"We will support every effort to understand the causes and impacts of yesterday's off-airport incident and we are committed to working closely with all stakeholders to ensure a thorough investigation," Woldbye adds.

Earlier, Woldbye was questioned on BBC's Today programme, where he described the fire at a substation near to Heathrow "unprecedented", adding he is "proud" of how the airport handled the incident.

Image source, Getty Images

Akshay Kaul, director general for infrastructure at Ofgem, says in the Energy Security and Net Zero department's statement that the authority "will not hesitate to take action."

He adds that Ofgem will work to ensure the National Energy System Operator's review "goes as far as possible to ensuring steps are put in place to avoid any repeat of an incident of this scale in the future".

The statement from Kaul also says that households and businesses "should be able to have confidence in the resilience of critical national infrastructure".

Image source, PA Media

Transport Secretary Heidi Alexander says it is "imperative" to "identify how this power failure happened and learn from this to ensure a vital piece of national infrastructure remains strong".

Within the statement from the Energy Security and Net Zero department, she warns "some disruption is expected" over the coming days and urges passengers to check the status of their flight before travelling.

Alexander adds that the incident caused "significant disruption" but praised emergency services for working "swiftly".

Image source, PA Media

We're now seeing a full statement from the Department for Energy Security and Net Zero, following Energy Secretary Ed Miliband's comments a short while ago.

The department says the National Energy System Operator's investigation will support efforts to "build a clear picture of the circumstances" surrounding the power outage at Heathrow and the UK’s energy resilience more broadly so that it’s prevented from ever happening again.

"The government’s Plan for Change is rebuilding Britain’s resilience, including boosting the country’s energy security with homegrown power. Separately, the resilience review led by the Cabinet Office is ongoing and is due to conclude in the Spring," the statement reads.

The statement also includes further comments from Energy Secretary Miliband, who says the government is "determined to do everything it can to prevent a repeat of what happened at Heathrow. This review will be an important step in helping us to do so, as we deliver our Plan for Change".

We'll bring you more from the department's statement in our next few posts.

A moment ago, we brought you news that the energy secretary has commissioned in investigation into the incident at Heathrow.

In a post on X, Ed Miliband writes: "The loss of power to the Heathrow area has caused major disruption to thousands of people and many businesses.

"We are determined to properly understand what happened and what lessons need to be learned."

He says he is working with Ofgem and has commissioned the National Energy System Operator to investigate the incident. Miliband says the investigation will look for "wider lessons" on energy resilience for critical national infrastructure.

Energy Secretary Ed Miliband has commissioned an investigation into the incident at Heathrow, to be carried out by the National Energy System Operator.

We'll bring you more on this in our next post.

Do airports of a similar size to Heathrow have different backup systems to respond to power outages?published at 15:03 Greenwich Mean Time 22 March

15:03 GMT 22 March

published at 15:03 22 March

15:03 22 March

Anna Holligan
Reporting from Amsterdam's Schipol Airport

Amsterdam’s Schiphol Airport is Europe's fourth-largest, serving approximately 67 million passengers annually.

Schiphol has faced power-related issues in the past, such as a voltage drop in Tennet's high-voltage grid in 2018, which led to disruptions in operations.

This incident resulted in improvements in monitoring of the emergency power generators and response systems. Schiphol is implementing energy storage solutions, such as iron flow batteries, to reduce reliance on diesel generators and improve environmental sustainability.

Despite these measures, like Heathrow, in the event of a major power substation failure Schiphol's systems might not be designed to power the entire airport indefinitely without external support.

Both incidents resulted in substantial disruptions to flight operations. At Schiphol in 2018, the power outage led to the closure of the airport, with flights delayed or cancelled, affecting thousands of passengers.

But the Schiphol outage in 2018 was due to a general power failure in the Amsterdam region, with the airport reopening after several hours once check-in systems were restored.

Both scenarios highlight the importance of robust backup systems and emergency response plans to mitigate the impact of power outages.

Image source, EPA

More than 100 flights through Heathrow have been cancelled today, one day after a power outage brought the airport to a standstill.

Although Heathrow Airport is now "fully operational", we've been keeping a tally of all the cancelled flights on Heathrow's departure and arrival boards today. British Airways has been particularly affected, but other carriers are seeing cancellations, too.

Here's what we found:

More than 30 departing flights cancelled

• According to Heathrow's live departure board, 34 flights that were due to leave the airport today have been cancelled
• These include several flights to domestic destinations, including Belfast and Edinburgh, and international flights to New York, Paris and Washington DC
• Around 16 departure flights are delayed today

You can check the status of your departing flight via your airline and on Heathrow's online departure board., external

More than 70 arriving flights cancelled

• According to Heathrow's live arrivals board, 71 flights expected to arrive at the airport today have been cancelled
• This includes flights from international destinations like Doha, Riyadh and Dubai, and to domestic locations including Manchester and Newcastle Upon Tyne

You can check Heathrow's arrival board on their website, external.

The term substation has been in the forefront of our coverage, as the disruption at Heathrow Airport yesterday was caused by a fire at a power substation in Hayes.

Elizabeth Orchard from the Institution of Civil Engineers explained to our colleagues at BBC Breakfast exactly what a substation is.

She describes it as a "stopping point" for electricity as it journeys from where it is generated to where it is used.

Large amounts of energy are used to enable the electricity to travel long distances. There are two types: transmission substations and distribution substations.

Transmission substations handle high-voltage electricity transmission over long distances, while distribution substations bring down the voltage for local distribution to homes and businesses.

Orchard adds that fires are "incredibly rare" as "substations are some of the best maintained infrastructure around the country".

We're now hearing from Labour MP Ruth Cadbury who tells the BBC that there is "a lack of power grid capacity" in the area surrounding Heathrow, with no new overhead lines expected until 2036.

She says it is too soon to tell whether this shortage had an impact on the closure of Heathrow Airport yesterday, after a substation fire caused a power outage.

Cadbury, who is chair of the Transport Select Committee, adds that the previous government has shown a lack of interest in Britain's infrastructure over the past 15 years.

She insists the Labour government is picking up on these issues but says it will take time to "ensure our key national infrastructure is fit for purpose".

Asked about plans for a possible third runway, she says it will take years but by that time "West London may have secured the additional grid capacity it needs".

In terms of mitigating the type of crisis we saw yesterday, she adds that Heathrow and airports in other countries will be "looking at their systems in the weeks to come".

BBC's Emma Barnett earlier put it to Heathrow's Chief Executive Thomas Woldbye that yesterday's full closure may impact passengers' trust in the airport - especially ahead of its controversial plans to build a third runway.

Woldbye said that he has "full trust in the fact the airport can build a third runway that is resilient".

Let's take a look at those plans for a third runway:

• In January, the government backed the expansion of the airport saying it could create 100,000 jobs, with Chancellor Rachel Reeves saying "a third runway is badly needed"
• A third runway would mean demolishing hundreds of homes, diverting rivers, and rerouting the M25 motorway
• The number of flights to and from the airport, currently capped at 480,000 a year, could go up to 720,000 - nearly 2,000 a day
• Heathrow told the BBC that it would eventually be able to serve up to 140 million passengers a year once the runway is operational

Future safeguarding against power outages brought into questionpublished at 13:17 Greenwich Mean Time 22 March

13:17 GMT 22 March

published at 13:17 22 March

13:17 22 March

Marc Ashdown
Business correspondent

Image source, EPA

In the end, Heathrow Airport was only out of action for 18 hours, but it left vital cargo - such as life-saving organs - stranded mid-transit. While passengers, pilots and planes have been scattered across Europe.

The airport's boss Thomas Woldbye said planes could have taken off and landed yesterday, but it was not safe to do so without back-up power to infrastructure such as runway lights, fuel systems and air bridges.

He insisted any airport would have responded in the same way, and said Heathrow uses as much power as a city and would need to install an expensive standalone generator to absolutely guarantee no power outages.

With one business leader labelling the UK a "laughing stock" over the incident, could this incident now weigh on its future investment plans?

Heathrow recently announced a multi-billion pound expansion plan, including revamping two terminals and adding a controversial third runway.

But the question of how to safeguard against damaging power outages has now entered the equation too.

We're seeing images showing passengers filing into Heathrow after it was announced that the airport is "fully operational" today.

Although flights to and from the airport have resumed, some airlines are warning passengers to expect delays.

Image source, EPA

Image source, EPA

Image source, EPA

Image source, Getty Images

Air India has just announced that their operations to and from Heathrow Airport have started again following yesterday's disruption.

"Today’s flight AI111 was on schedule and other flights, to and from London, are expected to operate as per schedule," it says in a statement.

Meanwhile, flight AI161 - which diverted to Frankfurt - "is expected to leave Frankfurt at 14:05 pm local time", the airline says.

Image source, PA Media

Farah Rafeeq, 24, says she is frustrated to miss part of her close friend’s wedding after the fire which closed Heathrow Airport on Friday.

She was due to travel with Singapore Airlines with her 32-year-old friend Niken Wulan, who is pregnant, to a wedding in Cambodia on Sunday.

The mass-cancellation of flights means they will now miss part of the ceremony.

They have found an alternative flight from Gatwick Airport with Turkish Airlines and Bangkok Airways that will get them to Cambodia for Sunday afternoon.

Farah tells the PA news agency today that the last few hours have been "nightmarish" because "it is one of our closest friends’ wedding and we have to travel for at least 20 hours to get there".

“We had to pay double the amount, between £600 and £700, for the new flight, and we had planned this trip for months and had hotels booked," she says.

“We are missing the morning ceremony but at least we can make it for the reception.”

As we continue to update you with the latest developments on Heathrow Airport, we're looking to hear from you.

Are you stranded at a different airport because of yesterday's closure or facing further travel delays?

You can get in touch with us on WhatsApp at +44 7756 165803 or via Your Voice, Your BBC News.