British Airways has suffered a data breach, with critical information on hundreds of thousands of its users being stolen by hackers.
British Airways says its website and app were compromised, allowing hackers to steal personal and financial details.
"We are 100 per cent committed to compensate them", BA chief executive Alex Cruz told BBC radio.
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. "No passport or travel details were stolen".
"The breach has been resolved and our website is working normally".
Financial and personal data has been stolen from potentially hundreds of thousands of British Airways customers who booked online in recent weeks, extending a run of embarrassing technological mishaps suffered by the United Kingdom flag carrier.
British Airways says the problem has been fixed and that its systems are no longer affected by the cyberattack.
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British Airways announced the news via Twitter, as well as contacting affected customers.
BA said it was investigating the vast breach "as a matter of urgency", while the National Crime Agency and National Cyber Security Centre are also assessing the hack. This month's data breach has not affected scheduled flights.
Shares in BA's parent, International Airlines Group, fell 3 percent in early trading.
Around 380,000 card payments were "compromised", it said.
It said in a recorded message that its security systems would likely stop any fraud as a result of the hack but anyone affected should look out for unusual activity on their accounts.
In July, the airline apologised after IT issues caused dozens of flights in and out of London's Heathrow Airport to be cancelled.
IAG also owns Spanish carriers Iberia and Vueling, as well as Irish airline Aer Lingus.