BA chief executive Alex Cruz says he will not resign and that flight disruption had nothing to do with cutting costs.
He told the BBC a power surge, had “only lasted a few minutes”, but the back-up system had not worked properly.
He said the IT failure was not due to technical staff being outsourced from the UK to India.
Mr Cruz said he was “profusely sorry” to the thousands of passengers still stranded at airports worldwide.
He said two thirds of passengers will have reached their destination by the end of the day.