A significant fire incident near Heathrow Airport led to its full closure and widespread disruption on March 21, 2025. The blaze, which erupted at a nearby electrical substation, knocked out power to Europe’s busiest airport and its backup systems. This unprecedented event resulted in chaos for hundreds of thousands of travelers, affecting flights globally and causing considerable economic impact.

The decision to declare Heathrow Airport closed was made in the early hours of March 21, following the fire that started late the previous night at the North Hyde electrical substation in Hayes. The fire involved a transformer with 25,000 liters of cooling oil, creating a major hazard and cutting off power supply to the sprawling airport, which uses as much energy as a small city.

The immediate impact of the Heathrow Airport closed announcement was severe. Over 1,300 flights were cancelled or diverted, affecting approximately 200,000 passengers. Many long-haul flights already in the air were forced to turn back or divert to other airports across the UK and Europe, leaving travelers stranded and airlines scrambling to reconfigure their networks.

While the London Fire Brigade worked for seven hours to bring the blaze under control, and power was eventually restored by the National Grid, Heathrow Airport closed for almost 18 hours. Airport executives later defended their decision, citing the need to safely power down and reboot hundreds of critical systems, emphasizing the complexity of restarting operations for such a massive hub.

The incident sparked questions about the resilience of critical national infrastructure. An independent review, known as the Kelly Review, was commissioned by Heathrow management to investigate the cause and response. This review noted that the fire was deemed a “low likelihood event” but highlighted lessons to be learned for future energy resilience.

The financial fallout was substantial, with airlines reportedly losing tens of millions of dollars due to cancellations and diversions. Beyond the airport, the power outage also affected thousands of homes and local businesses in the surrounding areas, underscoring the broader impact of the substation fire.