Willie Walsh, chief executive of International Airlines Group, BA’s parent company, said that the supply went down on Saturday morning but that the problem was compounded by an “uncontrolled” reboot of the system, which then knocked out the entire IT infrastructure.
The sudden return of power led to the loss of flight, baggage and customer communication information.
BA’s uninterruptible power supply is supposed to use multiple power sources, including a standby generator, to maintain a constant supply to BA’s two main IT centres near Heathrow.
IAG, the parent company of BA, which saw its share price fall sharply, said that the issue was not linked to any problem with the external supply provided by energy companies or outsourced IT suppliers in India.
BA chief executive Alex Cruz said the outsourcing of jobs was not to blame.
The carrier was unable to resume a full schedule until Tuesday and many passengers who had already checked in when the problem arose are still waiting to be reunited with their luggage.