Aer Lingus today said it was confident of winning a legal battle to force rival airline Ryanair to sell its stake in the company.
The carrier has lodged an appeal with the European Court of First Instance in Luxembourg.
If the case is successful the EU Commission will be given the power to order Ryanair to dispose of its 29.4 per cent stake.
John Sharman, Aer Lingus chairman, said the airline was determined to force its rival out.
"Aer Lingus is forging ahead with its plans for growth and refuses to be undermined by its competitor," he said.
"It is our intention to deal with the presence of Ryanair on our shareholder register decisively through short-term interim measures, as well as seeking a speedy permanent resolution from the Court of First Instance."
In October 2006 Ryanair launched a bold €1.48 billion bid for Aer Lingus just days after the former state-owned company was floated on the stock market.
The buyout was blocked by Europe but Michael O'Leary's budget airline eventually took its total holding to 29.4% last August — just shy of the 30 per cent threshold which would trigger an automatic takeover bid.
The European Commission previously ruled it does not have the legal authority to force Ryanair into a sell-off merger regulations.
But Aer Lingus said it was confident strict rules on mergers gives the Commission power to force Ryanair out and claimed the shareholding was part of the original takeover attempt.
Aer Lingus has also asked the Court to make an order to prevent Ryanair from interfering in the running of its business pending judgment on the appeal