Ryanair will hear this morning whether it's been successful in its latest efforts to prevent the UK Competition Commission from probing its near 30pc stake in Aer Lingus.
The UK's Court of Appeal is due to deliver its verdict on the long-running saga.
The carrier, headed by Michael O'Leary, has tried to thwart the Competition Commission for over two years from investigating its Aer Lingus holding.
The UK's Office of Fair Trading originally referred the Ryanair stake in Aer Lingus for a full investigation by the Competition Commission after determining that the larger carrier may be able to exercise "material influence over the commercial policy" of the former state-owned airline.
Britain's Competition Appeal Tribunal ruled in August that the European Commission had no jurisdiction over the minority shareholding in Aer Lingus, making it proper for British regulators to investigate. Ryanair went to the Court of Appeal to try and have that ruling overturned.
Ryanair has argued that when it launched its third bid for Aer Lingus this summer, the exclusive jurisdiction of the EU Commission to probe Ryanair's stake in its smaller rival had been triggered.
Ryanair's lawyer in the case asked the Court of Appeal last month whether it was "really sensible" to have two investigations going on at the same time.
But a lawyer for the Competition Commission argued that the "duty of sincere cooperation" required by national regulators in EU member countries "simply does not preclude the Competition Commission from continuing its investigation".
The Court of Appeal is due to deliver its ruling at around 10am today.
The EU's Competition Commission has already told Ryanair that it's unhappy with the extent of the remedies that have been proposed by the carrier in order to try and secure approval for being allowed to pursue an Aer Lingus takeover.
Mr O'Leary has said that he will consider legal action in Europe if competition watchdogs block the latest bid.
However, he has also said that Ryanair will consider selling its Aer Lingus stake in the event the buyout attempt is blocked.