Britain's National Grid said it reconfigured the network around a substation and restored power to the parts of Heathrow Airport connected to it on an interim basis.
Heathrow, one of the world's busiest airports, was completely shut down after a large fire at a nearby electrical substation knocked out power.
"The network has been reconfigured to restore all customers impacted, including the ability to resupply the parts of Heathrow airport that are connected to North Hyde," a National Grid spokesperson said.
"This is an interim solution while we carry out further work at North Hyde to return the substation and our network to normal operation."
Heathrow said on Friday that it still did not know when full power would be restored, adding that it would provide additional information whenever possible.
"We will provide an update when more information on the resumption of operations is available," a spokesperson for the airport said in a statement.
"To maintain the safety of our passengers and colleagues, Heathrow will be closed until 23h59 on 21 March," Heathrow Airport said in a post on X, adding that "passengers are advised not to travel to the airport and should contact their airline for further information."
The London Fire Brigade announced that a fire at an electricity substation in Hayes that broke out Thursday night and shut down the airport was under control.
Meanwhile, British Prime Minister Keir Starmer said in a social media post that he was receiving regular updates and that he was in close contact with partners on the ground.
