The fire that engulfed an electrical substation in March 2025, causing Heathrow Airport to close for over 12 hours, was attributed to a short circuit in an inadequately maintained transformer part, according to a report released by British government regulators. This incident disrupted over 1,000 flights at the major travel hub on March 21, cutting electricity to vital safety systems and leading officials to halt all air traffic for most of the day.
Authorities initially stated that the outage stemmed from a dramatic fire at the substation and ruled out terrorism or malicious acts. However, they had not revealed the causes behind the fire until now. The comprehensive 77-page report indicated that issues with a certain transformer component, known as a bushing, were first identified in 2018 but remained unaddressed, as maintenance scheduled for 2022 was deferred.
The report noted that the last time essential maintenance was performed on the troubled transformer, identified as SGT3, was back in July 2018 by National Grid Electricity Transmission, the operator of the substation. The report delineated that multiple attempts were made to arrange for necessary maintenance, but all were unsuccessful.
The power outage raised alarm among travelers, airline representatives, and even political leaders about the fragility of the UK's electrical grid. Prime Minister Keir Starmer expressed his "deep concerns" regarding the closure and emphasized the importance of elucidating the circumstances surrounding the incident.
Further findings from the report indicated that Heathrow's internal power systems were not adequately designed to quickly revert to alternative power from two adjacent substations that remained unaffected by the fire. Officials had underestimated the potential for a catastrophic power failure, making incorrect assumptions about the resilience of the wider electrical network.
The report concluded that the airport’s internal electrical distribution systems relied on manual switching and were not ready to efficiently utilize power from multiple sources in the event of such outages, raising essential questions about infrastructure preparedness in high-stakes environments like international airports.
Authorities initially stated that the outage stemmed from a dramatic fire at the substation and ruled out terrorism or malicious acts. However, they had not revealed the causes behind the fire until now. The comprehensive 77-page report indicated that issues with a certain transformer component, known as a bushing, were first identified in 2018 but remained unaddressed, as maintenance scheduled for 2022 was deferred.
The report noted that the last time essential maintenance was performed on the troubled transformer, identified as SGT3, was back in July 2018 by National Grid Electricity Transmission, the operator of the substation. The report delineated that multiple attempts were made to arrange for necessary maintenance, but all were unsuccessful.
The power outage raised alarm among travelers, airline representatives, and even political leaders about the fragility of the UK's electrical grid. Prime Minister Keir Starmer expressed his "deep concerns" regarding the closure and emphasized the importance of elucidating the circumstances surrounding the incident.
Further findings from the report indicated that Heathrow's internal power systems were not adequately designed to quickly revert to alternative power from two adjacent substations that remained unaffected by the fire. Officials had underestimated the potential for a catastrophic power failure, making incorrect assumptions about the resilience of the wider electrical network.
The report concluded that the airport’s internal electrical distribution systems relied on manual switching and were not ready to efficiently utilize power from multiple sources in the event of such outages, raising essential questions about infrastructure preparedness in high-stakes environments like international airports.
