Human error is being blamed for causing the British Airways IT outage that led to travel chaos for 75,000 passengers.
Willie Walsh, chief executive of BA owner International Airlines Group, said an engineer disconnected a power supply, with the major damage caused by a surge when it was reconnected.
He said there would now be an independent investigation “to learn from the experience”.
Walsh, appearing at the annual Iata agm in Mexico, said: “It’s very clear to me that you can make a mistake in disconnecting the power.
“It’s difficult for me to understand how to make a mistake in reconnecting the power.”
He told reporters that the engineer was authorised to be in the data centre, but was not authorised “to do what he did”.
IAG has commissioned an “independent company to conduct a full investigation” into the IT crash over the May bank holiday weekend and is “happy to disclose details” of its findings, Walsh said.
The name of the company involved had not been disclosed.
He apologised again for the incident, the BBC reported, saying: “When you see customers who suffered, you wouldn’t want it to happen to any airline or any business.”
He added: “I wouldn’t suggest for one minute we got communications right at BA, we didn’t.”
BA said: ”We are receiving many claims at the moment for EU compensation in relation to the bank holiday weekend disruption.
“We are bringing in extra staff to deal with them, and our aim is to authorise payment for all completed claims within 14 days of receipt.”