London's Heathrow Airport temporarily closes due to "significant power outage"

London's Heathrow Airport announced it will be closed Friday after experiencing a "significant power outage" due to a fire. 

"Due to a fire at an electrical substation supplying the airport, Heathrow is experiencing a significant power outage," Heathrow Airport said in a post on X, saying that "passengers are advised not to travel to the airport." 

It was unclear exactly how many flights were immediately impacted. The airport said it would be closed through midnight Friday local time.