Japan Airlines’ Customer Information System has been hacked.

It is possible that the hackers retrieved personal data for up to 750,000 of its frequent-flier program members.

The airline confirmed Monday it has found evidence of unauthorized access to its Customer Information Management System due to a virus attack on computer terminals within its network. The personal data of JAL Mileage Bank members are stored in the system.

The data that may have been leaked include the names, genders, birth dates, addresses, email addresses and places of work of JAL’s mileage program members.

The airline said there is no indication that the members’ passwords or credit-card numbers have been stolen.

JAL is part of Oneworld. Frequent-flier membership data are shared between members of the Oneworld group. Among the companies of the group are American Airlines, British Airways and Iberia .

A Oneworld spokesman said it was in contact with JAL, though initial indications were that no other members’ customers had been affected by the breach at JAL.