Bosses at London's Heathrow Airport have defended their response to a fire that shut down Europe's busiest air hub for almost a day, after the national energy system operator suggested the airport had enough electricity from other sources to keep running.
More than 1,300 flights were cancelled on Friday after a fire knocked out one of the three electrical substations that supply Heathrow with power.
Some 200,000 passengers had journeys disrupted and industry experts say the chaos will cost airlines tens of millions of euros.
Operations resumed at the airport after around 18 hours when Heathrow reconfigured its power supply.
The airport said it ran a full schedule on Saturday and Sunday, with 400,000 passengers passing through on 2,500 weekend flights.
The fire's impact raised concerns about the resilience of Britain’s energy system to accidents, natural disasters or attacks.
The government has ordered a probe into "any wider lessons to be learned on energy resilience for critical national infrastructure."
Counterterrorism police initially led the investigation into the fire, which came as authorities across Europe brace for potential attacks backed by Russia.
The head of the UK spy agency MI6 has accused Moscow of mounting a "staggeringly reckless" sabotage campaign against allies of Ukraine in its war against Russia's full-scale invasion.
Police however say they have found no evidence of foul play.
The investigation has been handed back to the London Fire Brigade, which said it was focusing on the substation's electrical distribution equipment.
Meanwhile, the utility company and airport executives are trading blame.
John Pettigrew, chief executive of the National Grid, told the Financial Times that "each substation individually can provide enough power to Heathrow" for the airport to stay open.
"Losing a substation is a unique event — but there were two others available," he said. "So that is a level of resilience."
Heathrow said it had worked to reopen "as soon as safely and practically possible."
"Hundreds of critical systems across the airport were required to be safely powered down and then safely and systematically rebooted," the airport said in a statement.
"Given Heathrow’s size and operational complexity, safely restarting operations after a disruption of this magnitude was a significant challenge."
Heathrow CEO Thomas Woldbye is also facing questions about why he put the airport's chief operating officer, Javier Echave, in charge of decision-making as the fire raged early on Friday.
UK Transport Secretary Heidi Alexander declined to back Heathrow management's decision-making, saying, "I don't have all the information that they had available when they made the decision."
"Safety should always be paramount, but, as I say, it was not my decision," she said in an interview with national public broadcaster, the BBC.
