SIPTU said today it strongly favoured a second terminal built and operated by the Dublin Airport Authority.
It added that it was only in the absence of a project by the authority that the union would support a proposition by the McEvaddy brothers for a privately-funded terminal on lands beside the airport at Huntstown.
The union added that this would also only be on the clear agreement that the McEvaddy project would not affect the quality of jobs at the new terminal.
SIPTU President Jack O'Connor has written to the Taoiseach, Bertie Ahern, supporting a second terminal run by the authority.
In his letter, Mr O'Connor acknowledged that the aviation branch of the union has engaged in exploratory discussions with Ulick McEvaddy.
But Mr O'Connor said the 'most sensible' option would be for the union to become involved in the authority's project.
