Heathrow Airport in London was plunged into chaos after a fire at an electrical substation shut down operations at one of Europe’s busiest air hubs, forcing the airport to cancel or divert more than 1,000 flights on Friday and removing a global linchpin of air travel.

Heathrow’s chief executive, Thomas Woldbye, described the disruption as “unprecedented,” telling reporters on Friday that the airport had lost power equal to that of a midsize city, and that though a backup transformer worked as it should, there had not been not enough to power the entire airport.

Some flights resumed late Friday, but Mr. Woldbye said, “We expect to be back in full operation, so 100 percent operation as a normal day” by Saturday.

The British authorities said the counterterrorism police would lead the investigation into the cause of the blaze, which broke out at an electrical substation in North Hyde, northeast of Heathrow. But the Metropolitan Police in London said later Friday, “After initial assessment, we are not treating this incident as suspicious, although inquiries do remain ongoing.”

It was too early on Friday to calculate the precise cost of the outage. But the outage raised questions about the resilience of Britain’s largest airport and why it appeared to be so reliant on a single electrical substation.

Efforts to douse the fire at the substation in Hayes, west London, on Friday.Credit…Agence France-Presse — Getty Images

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