SIPTU is refusing to rule out strike action by ground handling staff at Dublin Airport as part of a row over working conditions.
The row follows the awarding of a ground-handling contract for FlyBe and Turkish Airlines to Sky Handling Partners.
SIPTU says the company has refused to confirm whether the existing terms and conditions for around 56 workers will be honoured.
It is calling on the company to clarify its position and end the uncertainty facing the workers.