Aer Lingus management has urged cabin crew to accept a new pay deal when they vote on it tomorrow.
A ballot gets underway at Dublin, Cork, Shannon and Heathrow airports tomorrow and a result will be known by next Tuesday.
IMPACT, which represents 1,400 cabin crew, is recommending rejection of the deal.
IMPACT spokesman Bernard Harbor says if the offer is rejected, another wave of industrial action by Aer Lingus staff is on the cards.