The company has made industrial peace with unions a central selling point to potential investors. It emerged late last week that the pension deficit could be nearly twice as large as the 170m estimate that formed the basis for negotiations between unions and management prior to the flotation. An unreleased report by consultants Buck Heissman concluded the deficit could be as large as 329m, but was discounted by union officials.

At issue . . . and apparently still unresolved, despite the summer's lengthy negotiations leading to a 15 September pensions deal signed by unions and management . . . is who will have to pay extra in the event the pension comes up short . . .

the company or its employees.

"We would, from an IR [industrial relations] approach, expect the employer to make good any shortfall, " Siptu national industrial secretary Michael Halpenny wrote to Aer Lingus CEO Dermot Mannion on 8 August.

The letter concludes: "Since all of these issues impinge directly or indirectly on the IPO proposal . . . we would be obliged if you can update us on the situation to date." Halpenny told the Sunday Tribune this weekend that he still has not received a reply to that letter.

Aer Lingus top executives were travelling this weekend and unavailable for comment.

A spokeswoman could not say whether a reply had been made, written or otherwise, but pointed to the 380-page Aer Lingus IPO prospectus.

Under 'Risk Factors', the company says it believes it is not liable for any shortfall. It goes on to acknowledge that the government has been given "alternative legal advice" that Aer Lingus could be forced to make up a pensions shortfall, but having seen the advice they maintain their position.

Halpenny said this weekend that it didn't matter. "I told Mannion we don't give a flying flute about the legal situation, that the Pensions Board said it's a defined benefit scheme, and from an industrial relations point of view we'd come knocking on his door, in the event of a shortfall."