Fórsa has said that an agreement has been reached between it and Ryanair in the pilots' dispute.
The agreement has been reached following 22 hours of negotiations.
The proposed agreement will now go to ballot, with a recommendation for acceptance from Fórsa and its Ryanair pilot representatives.
The union has been asked by facilitator Kieran Mulvey to make no public comment while the ballot is conducted.
To-date the dispute has gone on for five weeks and resulted in some 100 Ryanair pilots taking strike action across five days. The pilots want a more transparent system to decide who gets first call on base transfers, holidays and promotions.
They are arguing for the system to be based on how long they are in the job.
In a statement Ryanair said that it will take the proposals to its board in due course after the Irish based pilots have voted on the signed agreement.
"The mediator, Kieran Mulvey, has asked both sides to refrain from further comment until the ballot has concluded and we will respect his wishes," Ryanair said.
Ryanair passengers have suffered hundreds of flight cancellations this summer because of protests by pilots over slow progress in negotiating collective labour agreements, hurting average fares at Europe's largest low-cost carrier.
The Irish airline endured its worst one-day strike earlier in August after a walk-out by pilots in five European countries disrupted the plans of an estimated 55,000 people at the height of the summer holiday season.
That included a fifth 24-hour walkout of the summer by around a quarter of its pilots in Ireland that prompted Ryanair to propose fresh talks with the help of a mediator that began last week and ended early on Thursday after a 22-hour session.
Ryanair employs more than 4,000 pilots, with around 350 of them based in Ireland.
(Additional reporting from Reuters)