Heathrow claims it had no choice but to suspend all flights on Friday after a fire at a nearby power substation, which started on Thursday evening, knocked out its main electrical supply.
It meant that around 1,300 flights were grounded, disrupting up to 300,000 passengers, costing airlines an estimated £20 million to £30 million.
Some flights resumed on Friday evening, but full operations didn’t resume until Saturday.
National Grid Chief Executive John Pettigrew described losing the substation as a ‘unique event’, but he said there were two other substations with enough power for Heathrow.
Responding to his comments in the national press, a Heathrow 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.
“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.
“Lessons can and will be learned, which is why we fully support the independent investigation announced by the Government yesterday.”
The National Energy System Operator will lead the investigation, while Energy Secretary Ed Miliband has said he will work with the power regulator Ofgem to ‘properly understand what happened and what lessons need to be learned’.
Transport Secretary Heidi Alexander said it is ‘imperative’ to ‘identify how this power failure happened and learn from this to ensure a vital piece of national infrastructure remains strong’.
Ofgem’s Director General for Infrastructure Akshay Kaul said the authority will ensure a review of the incident ‘goes as far as possible’ to ensure steps are taken to avoid a repeat of Friday’s shutdown.
