Fire Brigade members at the scene following a fire at an electrical substation at Heathrow on March 21. Photo: Leon Neal/Getty Images

London’s Heathrow Airport closed Friday after a fire at an electrical substation caused a major power outage and sparked travel chaos.

Why it matters: Heathrow Airport is the busiest airport in Europe and one of the best-connected travel hubs in the world. At least 1,350 flights that were scheduled to arrive at or depart from the airport have been affected so far, per the flight-tracking service Flightradar24.

• Counter-terrorism officers from London’s Metropolitan Police are also investigating the fire as a “precautionary measure,” per the BBC.

Driving the news: Heathrow said in a statement Friday that it was “experiencing a significant power outage” due to the fire at an electrical substation that serves the airport.

• It added that the airport would be closed through at least the end of the day.
• The airport also acknowledged in a separate statement that it was unclear when exactly the power would be restored, warning that it expects “significant disruption over the coming days,” the BBC reported.

Zoom in: The power outage from the fire has also impacted the local community.

• National Grid U.K. said Friday that roughly 5,000 customers were without power in the impacted area.

Go deeper: Some U.S. flights resume after outages disrupted businesses around the world