The comments come as the investigation into the power outage moves to focus on why the problem happened in the first place. The company’s own probe is now centring on why the power surge occurred – whether it was mechanical failure or human error.

For the first time, The Telegraph can reveal exactly what caused the airline’s operational and booking systems to collapse on Saturday.

It is understood that the investigation, being led by Mr Cruz himself with the help of external power supply specialists, is focusing on the uninterruptible power supply (UPS) to Boadicea House, one of two data centres in the environs of Heathrow airport.

In BA’s case, the UPS in question delivers power through the mains, diesel and batteries.

On Saturday morning, shortly after 8.30am, power to Boadicea House through its UPS was shut down – the reasons for which are not yet known.

Under normal circumstances, power would have been returned to the servers in Boadicea House slowly, allowing the airline’s other Heathrow data centre, at Comet House, to take up some of the slack.

But, on Saturday morning, just minutes after the UPS went down, power was resumed in what one source described as “uncontrolled fashion.” “It should have been gradual,” the source went on.

This caused “catastrophic physical damage” to BA’s servers, which contain everything from customer and crew information to operational details and flight paths. No data is however understood to have been lost or compromised as a result of the incident.

BA’s technology team spent the weekend rebuilding the servers, allowing the airline to return to normal operations as of today.

Sources close to the airline indicated that had the power been restored more gradually, BA would have been able to cope with the outage, and return services far more quickly than was the case.

The outage led to scenes of chaos for much of Saturday and Sunday at Heathrow and Gatwick and airports around the world, with 75,000 passengers affected by the problems.

The high-level investigation into the crisis – which analysts at Citibank today estimated could end up costing IAG as much as £100m – will now move to focus on why the UPS failed, and why power came back on so swiftly.

BA has to date struggled to publicly explain the problems behind the systems outage, at first suggesting that it was computer related, leading to questions of investment and outsourcing to India, and then confusing external commentators by talking of a power surge, without giving full details.

The airline and its parent company are now attempting to persuade customers and investors that the problem is in hand, and that operations have returned almost to normal.

Details of the early part of BA’s investigation follow comments from Theresa May, the Prime Minister, who went asked about the weekend’s delays said the problems were “predominantly a matter for British Airways.”

“It’s up to them to sort their IT out and to ensure that they are able to provide the services that people expect them to provide as British Airways,” she said during a general election campaign stop in Wolverhampton.

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 Shares in IAG fell 2.93pc on Tuesday, the first day of trading in London since the incident.