Members of IMPACT's cabin crew branch at Aer Lingus have voted in favour of industrial action.
The union has said its members have voted to take action, up to and including a strike, if the airline fails to agree a revised roster for short haul services and to implement acceptable time off after long haul flights.
The vote was passed with 97% in favour.
IMPACT said the ballot also called for action in the event of "further breaches by management of existing collective agreements, and if the company fails to implement an outstanding Labour Court recommendation on supervisors contracts".
IMPACT official Michael Landers said the result of the ballot indicated the depth of feeling about the issues contained in the ballot.
Cabin crew have sought a roster similar to those for pilots at the airline, of five work days followed by three rest days (known as a '5:3' roster pattern).
Currently, cabin crew can work up to 60 hours in a seven-day period, resulting in shift patterns of six working days and one rest day, followed by six more working days.
Cabin crew were also balloted for action in order to achieve agreement on the dispute with Aer Lingus on the Irish Airlines Superannuation Scheme. That ballot passed with just over 96% in favour.
IMPACT's cabin crew branch committee will meet in the coming days to discuss the options for industrial action.