An internal email sent by BillFrancis,Head of Group IT at British Airways' (BA) owner International Airlines Group (IAG), confirms that the shut-down had not been caused by IT failure or software issues, as claimed by workers' union which blamed BA's outsourcing of IT jobs to India for the crisis.
The email reveals that an investigation had found that an Uninterruptible Power Supply (UPS) to a core data centre at Heathrow Airport was over-ridden on Saturday morning.
"After a few minutes of this shutdown of power, it was turned back on in an unplanned and uncontrolled fashion, which created physical damage to the system, and significantly exacerbated the problem. This was entirely a problem relating to the power supply. It was not an IT failure, and there were no software issues," he adds.
The human error resulted inthe eventual systems failure, which was working perfectly until it was accidentally shut down, according to a report in 'The Times'.
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All information about flights, baggage and passengers was lost as a result of the sudden shutdown and incorrect reboot and travellers were left stranded over the bank holiday weekend with at least 700 flights cancelled at Heathrow and Gatwick airports.
The airline,which faces a bill of around 150 million pounds in compensation claims,has come under fire over its misleading compensation policy for those hit by the chaos.
The Association of British Insurers (ABI) had called on BA to change the wording because those caught up in disruption "should be able to claim compensation and refunds for any expenses as simply as possible, not passed from pillar to post".
"Those affected should seek compensation, and any refunds of expenses, in the first instance from British Airways," the ABI added.