The airline said on Wednesday that a loss of power to a United Kingdom data centre was "compounded" by a power surge that took out its IT systems.
"We had built up a tremendous reputation for excellence, with instantaneous recovery from any problems".
The GMB union has pointed to more than 200 redundancies made in the IT department under ferocious costcutting plans, which included bringing in staff from India on work visas.
Walsh apologized to customers that had been affected and defended Cruz's response to the outage, adding that the investigation into why the outage happened was continuing.
Speaking to Computer Weekly, Andy Lawrence, vice-president of research for datacentre technologies and eco-efficient IT, said what makes the case all the more puzzling is that most datacentres are created to cope with problems of this nature.
The airline said in a statement: 'There was a loss of power to the United Kingdom data centre which was compounded by the uncontrolled return of power which caused a power surge taking out our IT systems.
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According to statements given to various media outlets, the IT problems were caused by a power surge on Saturday morning at around 9.30am.
The IT failure at International Consolidated Airline's (LON:IAG) British Airways unit was caused by an "uncontrolled return of power", the Guardian has reported.
"We understand what happened, we're still investigating why it happened and that investigation will take some time".
The BA board is reportedly set to demand an independent inquiry into the IT shutdown after back-up systems also failed and the National Grid and local energy providers said there had been no supply issues on Saturday. IT services are now provided globally by a range of suppliers and this is very common practice across all industries and the UK Government.
BA claimed that this did not constitute an IT failure, but rather "it was an electrical power supply which was interrupted". "It was not an IT issue, it was a power issue". But the power was resumed minutes later in what was described as an "uncontrollable fashion", when it should have been gradual. It had nothing to do with outsourcing of IT.
BA said: "We are undertaking an exhaustive investigation to find out the exact circumstances and most importantly ensure that this can never happen again".