Ryanair has been accused of telling its Dublin-based pilots that they may be transferred to Luebeck in north Germany if they do not withdraw complaints of victimisation against the airline.
The President of the Irish Airline Pilots' Association, Evan Cullen, said he was concerned that pilots were being subjected to harassment and intimidation.
Mr Cullen denied Ryanair claims that the union had put pressure on pilots to join IALPA.
Ryanair is also allegedly demanding that pilots sign a bond making them responsible for the €15,000 cost of retraining, which would become payable if Ryanair is forced to negotiate with unions within the next five years.
In a statement, Ryanair described the allegations as incorrect and untrue and said it did not respond to trade union leaks to RTÉ.
