The IT failure at British Airways in May that left thousands unable to check in baggage cost it 65m euros (£58m), the airline's owner, IAG, has said.
BA said it was caused by an engineer who disconnected a power supply.
Despite the extra cost, IAG still managed to report a 13.8% increase in half-year operating profits to 898m euros (£804m).
Operating profits at British Airways rose to 741m euros from 631m euros a year earlier.
IAG, which also owns Aer Lingus, Iberia and Vueling, said it expected operating profit for the whole of 2017 to show a double-digit percentage improvement.
BBC News.