Following a mass cyberattack by an unknown hacker, British Airways has locked down the accounts of thousands of frequent airline customers.

The airline's systems were attacked by an automated process over the weekend, which used information obtained on the outside to find vulnerabilities in online security. The number of accounts affected by the hack was placed in the tens of thousands, but the company says no personal details have been jeopardized.

On Sunday, March 29, British Airways announced that it had frozen the accounts of frequent fliers for a few days, or until the problem is fixed. A spokesperson gave the following statement:

"We are sorry for the concern and inconvenience this matter has caused and would like to reassure customers that we are taking this incident seriously and have taken a number of steps to lock down accounts so they can no longer be accessed."

British Airways is currently unaware of any compromise to other areas of its systems, the spokesperson added. Though travel histories and credit card information wasn't believed to be affected, other personal information that may have been was not discussed.

The use of Avios, British Airway's frequent flyer miles system, has been suspended until further notice. In an email sent to customers and shared on FlyerTalk – a forum for discussing frequent flyer miles – British Airways said it had changed its customers' passwords.

The airline also urged holders of Executive Club accounts to change their login details if they used the same ones for their frequent flyer miles accounts.

While the use of Avios has been systemically suspended, customers who want to spend their miles will still be able to do so.

"In the meantime, however, if you wish to spend your Avios please contact us via your local Executive Club service center," read the email. "We will be able to reactivate your account by asking you some additional security questions."

While lifting the suspension will provide all customers with access to their Avios accounts again, those whose frequent flyer miles were completely wiped may have a slightly more difficult time recollecting what was erased.