AER Lingus' largest shareholder, Ryanair, has yet to decide whether it will back a deal to end a long-running pension dispute that is seen as key to the airline's valuation.
The pension scheme, which employees at Aer Lingus share with other aviation industry workers, has a deficit of more than €700m compared to Aer Lingus' market capitalisation of €880m.
A shareholder vote on a proposed one-off €191m payment into the pension pot is the last major obstacle to a resolution. Aer Lingus' share price briefly climbed 10pc when union members voted to back the deal earlier this month.
"We haven't made any decision yet. We will consider the EGM proposals and make a decision based on that," Ryanair Chief executive Michael O'Leary said.
Ryanair owns 30pc of Aer Lingus, but is currently appealing an order by Britain's Competition and Markets Authority (CMA) for it to cut its stake to 5pc.
O'Leary said he had not yet decided whether to ask for CMA permission to vote in the December 10 extraordinary general meeting.
But he said he still opposed in principle the approach Aer Lingus management were taking, saying the deal was "just another roll-over" by management to staff demands.
Analysts say the pensions issue has complicated attempts in recent years by Ryanair and the Government, who is a 25pc shareholder, to sell their stakes in the airline.
An Aer Lingus spokesman this month said no major shareholders had indicated how they would vote.
The airline is now examining how to use almost €400m of cash on its balance sheet following resolution of the pension issue.