Ryanair will know within weeks whether it will be forced to sell its stake in Aer Lingus by the UK's Competition Commission.
The watchdog said yesterday that it has restarted a long-running probe into the airline just days after the European Commission blocked Ryanair from buying Aer Lingus in its third takeover attempt of its smaller rival.
The Competition Commission is investigating whether Ryanair exerts undue influence over Aer Lingus through the near 30pc stake it holds in the former flag carrier.
In 2012, the UK's Office of Fair Trading (OFT) determined that Ryanair's stake in Aer Lingus "may give it the ability to exercise material influence over the commercial policy" of its rival. The OFT claimed that there was a "realistic prospect that its stake has resulted or will result in substantial lessening of competition on a number of Ryanair and/or Aer Lingus routes between the UK and Ireland".
The OFT then referred the matter to the Competition Commission for a full investigation.
Ryanair has attempted to halt the probe on a number of occasions via legal challenges, but without success. The Competition Commission put a stay on its investigation until the European Commission had delivered its ruling on the proposed Aer Lingus takeover this week.
It will deliver a preliminary ruling by May and a formal ruling on its investigation by July.
Ryanair boss Michael O'Leary has always dismissed the contention that the airline exerts any undue influence – commercial or otherwise – over Aer Lingus.
Aer Lingus has insisted that Ryanair's latest bid launched last year was "clearly motivated by a desire to derail the UK Competition Commission's investigation".
Aer Lingus chief executive Christoph Mueller has made no secret of the fact that he wants Ryanair removed as a shareholder from the group.
"It is unacceptable that our principal competitor has been allowed to remain as a significant shareholder on our share register even though the European Commission blocked their hostile takeover almost five years ago. This intolerable situation cannot be allowed to continue," he has previously said.
The best bet of seeing that achieved may now be through a Competition Commission decision. However, even if the commission orders Ryanair to sell its Aer Lingus stake, Ryanair will be able to appeal the ruling.
In 2011 the Competition Commission ruled that Stansted owner BAA should be forced to sell the airport to boost competition. That decision was challenged but last year BAA agreed to sell Stansted, Ryanair's biggest base, to the Manchester Airports for £1.5bn (€1.7bn).