Just over 1,400 Aer Lingus cabin crew will vote on a new pay deal today.
IMPACT, the union representing staff at Dublin, Cork, Shannon and Heathrow airports, has recommended its members turn down the deal.
The union said under the proposals, workers would have to work for 35 years in the job to earn a salary of £25,000.
Spokesperson Bernard Harbour said that the "very onerous" working hours proposed were another reason why many members were not in favour.
A formal vote on the issue is to be taken by cabin crew this afternoon.