The outsourcing of British Airways jobs was not to blame for a "catastrophic" IT failure that brought the airline's operations to a halt, its chief executive said.
BA was accused of greed after the GMB union suggested the disruption could have been prevented if the beleaguered airline had not cut "hundreds of dedicated and loyal" IT staff and contracted the work to India in 2016.
But the airline's chief executive Alex Cruz said this was not the case, adding that a full investigation would be conducted into the failure which affected 75,000 passengers.
He told Sky News: "I can confirm that all the parties involved around this particular event have not been involved in any type of outsourcing in any foreign country.
"They have all been local issues around a local data centre who has been managed and fixed by local resources."
Mr Cruz said: "On Saturday morning at around 9.30 there was indeed a power surge that had a catastrophic effect over some communications hardware which eventually affected all the messaging across our systems."
He added: "We will have completed an exhaustive investigation on exactly the reasons of why this happened. We will, of course, share those conclusions once we have actually finished them.
"We have no evidence whatsoever that there was any cyber attack of any sort."
Mr Cruz apologised "profusely" for the hardship caused to customers and insisted a similar incident would never happen again.
He further offered assurances that no customer data or any list, including terror watch lists, had been compromised by the glitch.
Mick Rix, national officer for aviation at the union, said at the weekend: "This could have all been avoided.
"In 2016 BA made hundreds of dedicated and loyal IT staff redundant and outsourced the work to India.
"BA have made substantial profits for a number of years, and many viewed the company's actions as just plain greedy."
BA has said it will run a full schedule at Gatwick on Monday and it intends to operate a full long-haul schedule and a "high proportion" of its short-haul programme at Heathrow.
However, the airports advised passengers to check the status of their flights before travelling.
On Saturday night travellers spent the night sleeping on yoga mats spread on terminal floors after BA cancelled all flights leaving the London hubs, while disruption continued into Sunday with dozens more services from Heathrow axed.
The IT outage had a knock-on effect on BA services around the world, while passengers who did get moving on the limited number of flights to take off from the UK reported arriving at their destinations without their luggage.
The disruption also hit transport systems on the ground, with hundreds of travellers flooding London's King's Cross station in hope of boarding a train north instead.
Experts predict the knock-on effect could continue for several days and BA is facing huge compensation costs, with reports suggesting the bill could top £100 million.
Mr Cruz said the airline was "committed" to following all compensation rules.