The High Court has granted Ryanair an injunction preventing a planned strike over the next two days by some of the airline's pilots based in Ireland.
Around 180 pilots who are members of the Irish Air Line Pilots' Association (IALPA), which is a branch of the Fórsa union, were due to take industrial action tomorrow and on Friday in a dispute over pay and conditions.
It follows a ballot of eligible IALPA members, which was passed by the overwhelming majority of those who took part.
Ryanair sought the injunction preventing Fórsa and 11 named individuals from proceeding with the work stoppage, which was due to get under way after midnight tonight.
During two days of High Court hearings, the airline argued a strike would be a breach of an agreement put in place following a series of strikes at Ryanair last year.
It requires any matters of dispute between the two sides to be referred to an independent mediator and to go through a dispute resolutions process before industrial action can take place.
Ryanair also claimed that the secret ballot that led to the vote in favour of industrial action was unlawful.
The union had strenuously denied this and told the court it had been conducted according to union rules and the law.
It also claimed that its current pay claim is not covered by the terms of the 2018 agreement.
Giving his ruling, Mr Justice Denis McDonald said he could not be satisfied based on the evidence that the laws around the conduct of a secret ballot leading to industrial action were complied with.
He said the evidence he had seen and heard did not address whether proper notice had been given to eligible members of Fórsa/IALPA on the voting arrangements.
While there was a gap in the evidence, the judge said he was not saying that the union had failed to properly inform its members.
He also said he was aware of the difficulties facing the defendants in responding to the claims made by Ryanair in the time frame.
He also said he could not exclude the possibility that a court might be persuaded at trial that the language and relevant factual backdrop to the 2018 agreement between Fórsa and Ryanair was intended to extend beyond last year's seniority dispute.
As a result, he said he had concluded that there is a fair question to be tried on the issue of the legal enforceability of that agreement.
He said it seemed to him that if Ryanair succeeded in proving at trial that the agreement was legally enforceable, the court would likely have to provide a permanent injunction.
Mr Justice McDonald said he would therefore grant the injunction to Ryanair on condition it gave an undertaking to bring the case to a full early hearing.
He also criticised some of the observations made by Ryanair in its affidavits, which he said were of a bare unsubstantiated kind.
He said he wanted to make it clear that he had no regard to those observations in making his decision.
Reacting to the ruling, Fórsa's spokesman Bernard Harbor said it had already informed its members who are directly employed Ryanair pilots that the industrial action was not going to proceed.
The union said it was going to study the judge's comments and consult its legal team.
As a result, he said it would not be appropriate to comment further until the judge had given his full interlocutory judgement.
In a statement, Ryanair welcomed the ruling by the High Court.
It called on Fórsa and IALPA pilots to return to mediation under Kieran Mulvey to resolve the dispute.
The airline said that all flights scheduled to depart on 22 and 23 August will operate as normal.