London Heathrow Airport fire in March: Fire 'probably' caused by unrepaired transformer leak

The fire caused chaos at Europe's largest airport. The fire in an electrical substation, which shut down London Heathrow Airport on March 21, was "probably" caused by an unrepaired leak in a key component, the National Energy System Operator (NESO) concluded on Wednesday, July 2.

The flames are believed to have started due to "a major failure in one of the transformer's high-voltage sockets [an insulating component, editor's note] ," probably "caused by infiltration," which led to a short circuit, the organization wrote in its investigation report. "A high humidity level in one of the sockets" had been detected in 2018, but "appropriate mitigation measures for its severity [had] not been taken," it noted.

Heathrow Airport, one of the world's busiest , remained closed for a whole day, causing a chain reaction to global air traffic, with hundreds of flights canceled or diverted.

"A combination of outdated regulations, inadequate safety mechanisms and the failure of [power network operator] National Grid to maintain its infrastructure led to this catastrophic power outage," a Heathrow spokesperson said. "We expect National Grid to carefully consider what steps it can take to prevent a similar situation from happening again," he added.

A National Grid spokesperson acknowledged there were "important lessons to be learned" from the incident, saying the utility had "implemented a comprehensive inspection and maintenance program" and specific measures since the fire.

Built in 1946, Heathrow is the largest of the five airports serving the British capital. In January, it received government approval to build a third runway by 2035.