A detailed timeline of the events surrounding the unprecedented day-long blackout that hit London’s Heathrow Airport has been set out by the National Energy System Operator, as scrutiny of grid security intensifies.
Heathrow was plunged into chaos on March 21 after a fire at the nearby electrical substation cut off its power, leading to hundreds of canceled flights. Backup systems allowed for some planes to land but didn’t allow for full operations.
NESO said in an interim interim report on Thursday [May 8] that investigations are still ongoing to find the “root cause” of the fire, but noted that police have found no evidence to suggest the incident was “suspicious in nature.” In its final report, NESO expects to make recommendations on the resilience of UK energy infrastructure, and how those systems are restored following disruptions.
Lawmakers, airline executives and the flying public have since questioned how one of the country’s most vital pieces of infrastructure could become vulnerable to a single point of failure. Scrutiny of power grid resilience has ramped up after last month’s massive blackout in Spain and Portugal left about 50 million people without electricity. The government in Madrid is still investigating the exact causes for the outage.
NESO is still looking into the maintenance history of some assets involved and at how different parties planned for this type of incident. Two of the transformers at the North Hyde substation are still off line following the fire.
“We now await the full report to understand what happened and learn lessons to strengthen UK energy resilience and protect our critical national infrastructure,” UK Energy Secretary Ed Miliband said.
Photograph: Firefighters douse an electrical substation following a fire near Heathrow Airport in March 2025; photo credit: Leon Neal/Getty Images
Related:
- Why Restarting a Power Grid After Massive Collapse Is So Hard
- Heathrow Shutdown Raises Concerns Over Contingency Planning
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