Aer Lingus cabin crew are balloting for strike action in a row over rosters which triggered a stoppage at the airline last year.
The move comes as the Government is considering whether to sell its 25% stake in the airline to IAG, though it is understood that the takeover bid is not on the agenda for tomorrow's cabinet meeting.
The IMPACT trade union, which represents most cabin crew, has issued ballot papers to members outlining a number of grievances which will trigger industrial action if not addressed by management.
They include the failure by management to introduce a "five day on, three day off" roster and what it calls the outsourcing of cabin crew work on the Shannon Boston route.
Earlier this year, the Labour Court ruled that management did not have to introduce the 5/3 roster as it would necessitate significant additional cost.
Cabin crew have been unhappy with that ruling and are now threatening strike action if a trial 5/3 roster is not implemented.
They are also concerned about Aer Lingus hiring in a larger 767 plane with American crew members to operate the route between Shannon and Boston for twelve weeks over the summer - which it describes as outsourcing without agreement.
In a letter accompanying the ballot paper, IMPACT Assistant General Secretary Michael Landers and cabin crew representative Angela McNeela say the cabin crew need to send Aer Lingus a strong message that cannot be ignored so that outstanding issues from last year's strike can be resolved.
They say they will no longer tolerate disrespect, and that only by voting for strike action will cabin crew get the company's attantion.
The ballot motion is for industrial action up to and including strike action if Aer Lingus takes any steps to outsource cabin crew work to non-Aerlingus staff or to offshore cabin crew work without union agreement.
It is also seeking the implementation of a trial 5/3 roster, and what it calls acceptable time off arrangements.
The ballot is expected to take three weeks.