Former chief financial officer of Aer Lingus, Brian Dunne, is believed to be the airline's leading target to replace Dermot Mannion as head of the company.

Meanwhile Siptu is to serve a claim on the carrier to have some of its €654m of cash diverted to shore up the airline's pension fund.

Dunne, who holds a senior position with Ace Aviation Holdings, the owner of Air Canada, is the leading contender if he agrees to return to Ireland, company sources told The Sunday Tribune. However Sean Coyle, who left Ryanair to become the carrier's finance director, is the strongest internal candidate.

A shortlist is to be drawn up shortly and Dunne is expected to be sounded out about his willingness to take on the role. A chartered accountant who was involved in re-structuring the company with former CEO Willie Walsh, Dunne is seen as the leading contender.

"He would be the ideal man, in that he already knows the company, knows its challenges and also has broad international aviation experience," an industry source said.

However, it is understood Dunne was sounded out about taking up his old position, later taken by Coyle, last year and showed no willingness to re-join Aer Lingus.

Meanwhile Siptu is expected to shortly serve a claim on the airline in an attempt to get it to transfer some of its cash resources into the multi-employer pension scheme of which Aer Lingus workers are members.

Aer Lingus will insist that it has no legal obligation to make additional contributions to this scheme, which is shared by workers from the Dublin Airport Authority and SR Technics.