SIPTU, Aer Lingus's largest trade union, is to embark on a consultative process with its 5,000 workers in the State-owned airline following an exploratory meeting on the flotation of the company last night with the Minister for Public Enterprise, Ms O'Rourke.

While the trade union IMPACT, which represents the airline's pilots and middle management, is likely to seek a additional 15 per cent stake in the company in an Employee Share Option Plan (ESOP) - on top of the 5 per cent already owned by staff - SIPTU has yet to consult its workers on the matter.

Ms O'Rourke is understood to be prepared to grant ownership of an additional 9.9 per cent stake only, matching the share of Eircom held by its workers.

The Minister is expected to appoint corporate advisers for the flotation later this week. Once the advisers are in place, the unions are expected to develop a joint strategy for the formal negotiation of an ESOP.

But other issues, such as the timing of the enabling legislation for the flotation, expected this autumn, and changes to pension arrangements at the company, which are currently being reviewed by a task force, are likely to be discussed first.