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Heathrow’s chief executive has said it could cost about £1bn to install a more “resilient” power system to help avoid a repeat of the outage that forced the airport’s closure last week, and warned airlines could end up paying through higher charges.

In his first detailed explanation of the disruption which involved the cancellation of more than 1,300 flights, Thomas Woldbye defended Heathrow’s handling of the outage, but admitted he was “frustrated” that he was asleep as the crisis unfolded.

He told the Financial Times he was convinced the airport had no choice but to close in the early hours of Friday morning last week on safety grounds.

He accepted Heathrow needed to review whether it could have been more nimble and reopened more quickly, which could have minimised the chaos that affected more than 200,000 travellers.

“It’s a relevant question,” Woldbye said. “And I’ll start out by saying that, you know, we don’t profess to be 100 per cent perfect.”

Heathrow closed after a massive fire at a nearby electricity substation caused a power outage at the airport. Flights bound for Europe’s busiest hub had to divert to other airports, and Heathrow did not fully reopen until more than 24 hours later.

The scrutiny on Heathrow deepened after John Pettigrew, chief executive of National Grid, which operates the UK’s high-voltage transmission network, said power had always been available to the airport from two other nearby substations which were unaffected by the blaze.

The delay in reopening the airport was caused by Heathrow’s engineers having to reconfigure its power supply to take electricity from the other two substations, and then test that all its critical safety systems were working properly.

Woldbye said the airport would now assess whether it is possible to install a “fully resilient” power system which would allow it to quickly switch between power sources. He said it was not clear if this was possible, but that it might cost upwards of £1bn if it is.

Other options include buying more generators to power more of the airport during outages. Heathrow’s current diesel generators only power safety-critical parts of the operation such as the control tower during outages.

The airport’s regulatory model allows it to recoup its capital expenditure from the landing charges it levies on airlines, which are ultimately passed through to passengers in ticket prices.

Woldbye said Heathrow faced a balancing act as it assesses how much the airport should spend on improving its resilience.

“We need to look at our resilience . . . but how far up the supply chain do we need to go, and how much would that cost?” he added.

“That’s a dialogue we have to have with our airlines, because they are deeply involved in our investments . . . which has an influence on our charges. That’s a very big discussion.”

The Danish executive has come under scrutiny after the Sunday Times reported that he went to bed as the fire burned, leaving his chief operating officer Javier Echave to make the decision to close Heathrow at about 2am on Friday morning.

But Woldbye said he had gone to bed at around 11pm, before news of the fire emerged, and that his colleagues had tried to reach him but could not get through.

“This is slightly frustrating, but I went to bed before it happened,” he added. “Somebody gave me a call which somehow did not go through. I slept through part of the night, until I woke up early in the morning and realised what had happened.”

But Woldbye insisted that Heathrow’s emergency plans, including its gold command response team, had worked effectively.

“My job as CEO is not to lead every single crisis,” he said. “My job is to make sure that there is a resilient organisation that, given any condition, will be able to take the right decisions for the airport, and make sure that we do the right thing.

“And that’s what we have. I just want to underline that our gold command system was working the way it should.”

Woldbye said decisions over his future were for the Heathrow board, but that its members had indicated they will support him.   

Heathrow’s own review into the handling of the electrical failure from Ruth Kelly, a board member and former UK transport minister, is expected by May. The government has launched its own probe.

Airlines have criticised Heathrow for its lack of resilience, and on Thursday Luis Gallego, chief executive of British Airways owner IAG, said he expected the disruption to cost his business “tens of millions” of pounds.

Woldbye did not rule out compensating airlines, but said he wanted to wait until there are more details on “exactly what happened”.

“Having lost a day in the airport’s history is not something we are overall proud of or happy with, but I don’t think it changes the fact that Heathrow has been operating excellently for many, many years,” he added.

“I really regret this happened on my watch. This is not something I take lightly . . . I am truly frustrated about what happened . . . and of course I would like to have done it better.”