SITPU President Mr Jack O'Connor has written to the Taoiseach restating the union's decision to support a second terminal at Dublin Airport.
In the letter to Mr Ahern he said the Civil Aviation Branch of SIPTU had engaged in "exploratory discussions" with Mr Ulick McEvaddy and others with a view to building a second terminal.
Mr McEvaddy, part owner of Omega Air, also owns a large land bank at Huntstown near the airport.
Mr O'Connor added that a separate company would be established to handle the workers' interests and the union would not be directly involved.
However, Mr O'Connor added that this was a last option and would only be supported "if the preferred and most sensible option, a Dublin Airport Authority project, is ruled out by the authorities.
"It is my honest belief that all the confusion surrounding this important issue would be dispelled very rapidly if the authorities were to make a decision in favour of the preferred option of a second terminal owned and operated by the Dublin Airport Authority," he added.