Heathrow Airport had “enough power” from remaining substations despite Friday’s shutdown, the chief executive of National Grid has said.
John Pettigrew said two substations were “always available for the distribution network companies and Heathrow to take power”.
Flights were halted after a fire knocked out an electricity substation in Hayes on Thursday evening, and were not able to resume until Friday evening.
In his first comments since the disruption, Mr Pettigrew told the Financial Times: “There was no lack of capacity from the substations.
“Each substation individually can provide enough power to Heathrow.”
The chief executive of the electricity and gas utility company added: “Two substations were always available for the distribution network companies and Heathrow to take power.
“Losing a substation is a unique event — but there were two others available.
“So that is a level of resilience.”
In response to the comments, a Heathrow Airport spokesperson said: “As the National Grid’s chief executive, John Pettigrew, noted, he has never seen a transformer failure like this in his 30 years in the industry.
“His view confirms that this was an unprecedented incident and that it would not have been possible for Heathrow to operate uninterrupted.
“Hundreds of critical systems across the airport were required to be safely powered down and then safely and systematically rebooted. Given Heathrow’s size and operational complexity, safely restarting operations after a disruption of this magnitude was a significant challenge.”
Heathrow chief executive Thomas Woldbye had said a back-up transformer failed during the power outage, meaning systems had to be closed in accordance with safety procedures so power supplies could be restructured from two remaining substations.
A report by consultancy firm Jacobs more than 10 years ago found a “key weakness” of Heathrow’s electricity supply was “main transmission line connections to the airport”.
The document, published in 2014, stated “outages could cause disruption to passenger, baggage and aircraft handling functions”, and “could require closure of areas of affected terminals or potentially the entire airport”.
In its appraisal of operational risk at the airport, Jacobs said provision of on-site generation and other measures to ensure resilient supply appeared “to be adequate” to enable Heathrow “to withstand and recover from interruptions to supply”.
It added that the airport operated “within risk parameters that are not excessive or unusual for an airport of its type”.
Energy Secretary Ed Miliband has ordered the National Energy System Operator to “urgently investigate” the power outage caused by the substation fire, and is working with Ofgem and using powers under the Energy Act to formally launch the grid operator’s investigation.
The National Energy System Operator (Neso) is expected to report to the Department for Energy Security and Net Zero and Ofgem with initial findings within six weeks.
Counter-terrorism officers from the Metropolitan Police initially led the investigation, but the force said the fire is not believed to be suspicious so London Fire Brigade is now leading the probe which will focus on the electrical distribution equipment.
Meanwhile, an internal review of the airport’s crisis management plans and its response to Friday’s power outage will be undertaken by former transport secretary Ruth Kelly, who is an independent member of Heathrow’s board.
A Heathrow spokesperson said: “In line with our airline partners, our objective was to reopen as soon as safely and practically possible after the fire.
“The emergency services and hundreds of airport colleagues worked tirelessly throughout Friday to ensure the safe reopening of the airport.
“Their success meant that over the weekend, we were able to focus on operating a full schedule of over 2500 flights and serving over 400,000 passengers.”
British Airways said it was expecting to run a “near-full schedule” on Sunday and passengers should go to the west London airport as normal unless told otherwise.
The airline said it operated about 90% of its scheduled flights on Saturday when Heathrow said it was “open and fully operational”.
Heathrow is Europe’s largest airport, with more than 83.9 million passengers travelling through its terminals in 2024, and around 200,000 passengers were affected by Friday’s closure.
