close video Massive fire seen at London Heathrow Airport

London Heathrow Airport will be closed all day Friday, March 21, after a fire caused a “significant” power outage. (CREDIT: Sergio Vilelas via Storyful)

One of the busiest airports in the world will be closed all day Friday after a fire caused a "significant" power outage.

London Heathrow Airport (LHR) said it is "experiencing a significant power outage across the airport due to a large fire at a nearby electrical substation."

"Whilst fire crews are responding to the incident, we do not have clarity on when power may be reliably restored. To maintain the safety of our passengers and colleagues, we made the decision to close Heathrow until 23h59 on 21 March 2025," a spokesperson for the airport told Fox News. 

"We expect significant disruption over the coming days and passengers should not travel to the airport under any circumstances until the airport reopens," the spokesperson added. "We will provide an update when more information on the resumption of operations is available. We know this will be disappointing for passengers and we want to reassure that we are working as hard as possible to resolve the situation."

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London Heathrow Airport in London, England, will be closed all day Friday, March 21, after a fire caused a “significant” power outage, the airport said. (Sergio Vilelas via Storyful / Storyful)

The airport was anticipating up to 291,000 passengers on a total of 1,351 flights on Friday, Reuters reported.

Passengers have been told to contact their individual airline for further details on new flight times.

Airlines began issuing statements on Friday addressing how the 24-hour closure would impact their passengers and flights to and from the airport.

British Airways said the disruption "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 London Fire Brigade said approximately 70 firefighters and 10 engines responded to the fire just before midnight on Thursday at the electrical substation on Nestles Avenue in Hayes.

"This was a very visible and significant incident, and our firefighters worked tirelessly in challenging conditions to bring the fire under control as swiftly as possible," Assistant Commissioner Pat Goulbourne said in a statement, adding that the fire was under control by 6:30 a.m.

The London Fire Brigade said around 70 firefighters responded to the substation fire on Nestles Avenue in Hayes before midnight on Thursday. (London Fire Brigade/X / FOXBusiness)

Though there were no injuries, the brigade said 29 people were evacuated from neighboring properties and 150 others were evacuated from a 200-meter perimeter that was established out of precaution. 

"The fire has caused a widespread power outage, affecting many homes, local businesses, and Heathrow Airport. While power has been restored to some properties, we continue to work closely with our partners to minimise disruption," Goulbourne said.

The fire brigade will remain at the scene throughout the day to assist the National Grid, which owns the high-voltage electricity transmission network in England and Wales.

Residents are advised to keep doors and windows closed as smoke will linger in the area.

An electrical substation that supplies London Heathrow Airport caught on fire on Friday, causing a significant power outage that shut down the entire airport for the day. (BENJAMIN CREMEL/AFP via Getty Images / Getty Images)

Secretary of State for Transport of the United Kingdom Heidi Alexander said she is aware of "the fast-moving situation" at Heathrow and receiving updates on progress.

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"I'm grateful to emergency services responding to the fire, and National Grid for working to restore power to the airport and homes," Alexander wrote on X. "I’d urge passengers not to travel to the airport, and contact their airline."

Fox News' Simon Owen contributed to this report.