Ryanair pilots are voting on proposals that could lead to strike or some other form of industrial action.
Pilots at the airline are campaigning for a new collective bargaining system to replace the employee representative councils that negotiate for staff at each Ryanair base.
However, Ryanair refuses to deal with the new organisation, the European Employee Representative Council, which wants to negotiate for its 4,000-plus pilots with the support of unions in countries where the company operates.
Members of the Irish Airline Pilots’ Association (IALPA) who work for Ryanair are understood to be voting on a ballot for industrial action up to an including strike.
Ryanair pilots who are members of other European unions are also engaged in similar procedures. All of them are said to be following legal advice to ensure that they comply with local industrial relations legislation.
It was not clear if the vote would lead to any immediate action. Sources indicated that pilots may target peak flying next summer rather than winter when demand is lower.
Reports this week stated that members of Italian pilots' union, Anpac, in Ryanair were planning to stop work for four hours on December 15th. However, the airline said previous threats of stoppages in Italy had all been cancelled.
Ryanair's chief people officer Eddie Wilson this week warned that if pilots in Dublin supported any action, the company would withdraw benefits tied to its existing collective agreement. He added that it could move craft from its Dublin base.
Ryanair said on Thursday that it did not pay any attention to correspondence from Aer Lingus pilots. The company maintains that IALPA is an Aer Lingus pilots' union. However, the association has said that its 1,200 membership reflects the fact that Ryanair is Ireland's second-biggest employer of pilots.
Mr Wilson's letter says that pilots at Ryanair's Belfast, Cork and Shannon bases recently agreed to pay increases of €22,000 a year for captains and €11,000 for first officers, along with other benefits.
Ryanair does not recognise unions but does not ban staff from joining them. It points out that the Supreme Court has approved its existing collective bargaining system.
Meanwhile, Ryanair's chief commercial officer, David O'Brien, said on Thursday that the airline was pressing the European Commission to make available take-off and landing slots in German airports vacated by insolvent rival Air Berlin. The carrier is seeking to establish new bases in Germany.