The airline promised to reimburse any financial losses suffered by customers directly because of the theft of this data.
The airline discovered on Wednesday that bookings made between August 21 and September 5 had been infiltrated, according to Reuters.
"The breach has been resolved and our website is working normally".
The airline had launched an investigation and notified police and other relevant authorities.
Chief executive Alex Cruz says the company is "100% committed" to compensating customers who have had financial information stolen.
"The moment we found out that actual customer data had been compromised, that's when we began an all out immediate communication to our customers".
British Airways have advised customers to contact their banks or card providers.
The airline added that customers due to travel could check in online as normal.
British Airways informed customers affected by the attack on Thursday, Cruz said.
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While this is certainly bad for both British Airways and its customers, things could have been worse.
Some angry travellers complained to Britain's Press Association that they had already noted bogus activity on credit cards that had been used to make British Airways bookings during the time when the breach was undetected.
"Atrocious that I had to find out about this via news and twitter", he tweeted.
"Sadly this data breach is likely to knock back its efforts". But what you do after you call the bank?
"Terrible handling of the situation as I've still not received an email from BA!"
"IT issues are not only affecting BA, but also in the wider airline industry".
Some 75,000 passengers were left stranded after a glitch forced the airline to cancel almost 726 flights over three days.
Almost 400,000 card payments have been affected (Picture: Getty Images)Which flight bookings were affected by the hack?