International Consolidated Airlines Group's (LON:IAG) share price has fallen into the red in London this Monday as it emerged that the company is facing a hefty fine over last year's theft of British Airways customers data. The breach affected bookings made between August 21 and September 5 last year. As of 09:06 BST, IAG's share price had given up 0.92 percent to 452.30p. The shares are underperforming the broader UK market, with the benchmark FTSE 100 index having climbed into positive territory and standing 0.17 percent higher at 7,565.74 points. IAG faces hefty fine IAG announced in a statement this morning that it had been notified by the Information Commissioner's Office (ICO) that it intends to issue the airline with a penalty notice under the UK Data Protection Act, over the theft of customer data from British Airways' website.