Aer Lingus pilots are set to strike over plans to pay colleagues based in Northern Ireland less money than those in the Republic of Ireland.
All of Aer Lingus's air routes will be affected
The Irish national carrier last week announced 100 new jobs with the launch of new flights from Belfast.
However, it did not dispute claims that employees at its new Belfast hub would not be paid the same rates as staff south of the border.
Almost 500 pilots are to stage a strike next Tuesday and Wednesday.
The pilots' union said it would not allow Belfast based pilots to be treated as "second class citizens", according to Irish state broadcaster RTE.
It is understood Aer Lingus is seeking to recruit up to 30 pilots for its Belfast operation, as part of a £100m investment.
It is expected all of Aer Lingus's air routes will be affected by the industrial action.
The decision was taken at a meeting of members of the Irish Airline Pilots' Association branch of IMPACT at Dublin Airport on Monday.
Aer Lingus's Belfast venture means that flights between Shannon and Heathrow will stop with at least 40 resultant job losses anticipated.
In a statement, Aer Lingus said it was "angry and disappointed that pilots would choose to attack customers in an act of self-centred brinkmanship".
"The company has been in negotiation with its pilots for some time now on a range of efficiencies that are essential to maintain competitiveness.
"The recent announcement of the Belfast base is an entirely separate matter."
It added: "Aer Lingus management is currently working on alternative arrangements and contingencies for customers on the days of the proposed strike actions.
"Customers are advised that they are likely to face severe disruption."