The incident relates to a flaw in a piece of software called MOVEit Transfer
Aer Lingus has confirmed that around 5,000 of its employees have been affected by a cyber attack that has compromised personal information.
The airline is among a number of global companies which has notified staff about the cyber attack. Aer Lingus also says that a "significant but lesser number of former employees" have also been affected.
The incident relates to a flaw in a piece of software called MOVEit Transfer, used by thousands of companies globally to transfer files, which could be exploited by cyber criminals.
Companies using the software were urged last week to take immediate action.
The UK's leading payroll provider Zellis said that eight of its customers have been impacted by the "global issue", which may have exposed personal information, including names, addresses, and banking details.