London’s Heathrow airport has shut down after having its power crippled by an immense fire at a nearby electrical substation, throwing thousands of global flights into chaos. Heathrow announced that it will remain closed until at least midnight on Friday “to maintain the safety of our passengers and colleagues,” and that there will be no flights operating at the airport during this time.

“Due to a fire at an electrical substation supplying the airport, Heathrow is experiencing a significant power outage,” Heathrow airport posted to X. “Passengers are advised not to travel to the airport and should contact their airline for further information.”

1,357 flights were scheduled to land or take off from Heathrow today according to flight tracking website FlightRadar 24. The airport handles an average of 220,000 passengers per day, making it the busiest in Europe and ranked fourth globally. At least 120 flights have already returned to their origin or been diverted to alternative airports, with The Guardian reporting that flights from Toronto, Atlanta, Bridgetown, Barbados, Boston, Orlando, and Newark have been redirected to Ireland due to insufficient capacity at London’s other airports.

”We expect significant disruption over the coming days and passengers should not travel to the airport under any circumstances until the airport reopens,” Heathrow said in a statement to Sky News. “We do not have clarity on when power may be reliably restored.”

Travel journalist Simon Calder told BBC News that this is the first time Heathrow airport has been fully closed since the disruption caused by the Eyjafjallajokull volcano eruption in 2010. “This is the busiest day of the week at the busiest airport in Europe. Fifteen years ago was the last time we saw the skies close down at Heathrow.”

Images of an empty Heathrow airport have also started to appear online.

Heathrow is the main base for its biggest carrier, British Airways. In a statement on X, the airline said that the closure will “clearly have a significant impact on our operation.” We have asked Heathrow airport for more information regarding when regular operations are expected to be restored.

It’s currently unclear what caused the fire at the electrical substation located about 1.5 miles away from Heathrow airport. More than 16,000 homes that are also supplied by the substation have been similarly impacted by power outages. The London Fire Brigade said the blaze has since been brought under control after 70 firefighters were deployed to the substation, and that the cause is now under investigation.