"From 22:58 BST August 21 2018 until 21:45 BST September 5 2018 inclusive, the personal and financial details of customers making bookings on our website and app were compromised. The breach has been resolved and our website is working normally. We have notified the police and relevant authorities," the company said in a statement.
British Airways CEO and chairman Alex Cruz expressed regret over the incident and apologized to customers.
"We are deeply sorry for the disruption that this criminal activity has caused. We take the protection of our customers' data very seriously," Cruz said.
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International Airlines Group, the parent company of British Airways, is conducting an urgent investigation into the incident.