Unions at Aer Rianta have notified the company of plans to ballot members for industrial action that could bring strike action at Dublin, Cork and Shannon airports.
Balloting is to start next week and it is thought a result will be known on by September 6th.
The unions, which represent almost 2,000 workers, are SIPTU, MANDATE, IMPACT and the TEEU.
The unions' decision is thought to have followed a meeting with Aer Rianta management earlier this week at which the company said it could not guarantee employees' pay or employment terms beyond the next 12 months.
There was an angry reaction by trade unions last month to the plan by the Minister for Transport, Mr Brennan, to set up the airports in Dublin, Shannon and Cork as independent entities owned by the State.
Mr Brennan has insisted that no jobs will be lost and says the privatisation of the airports is not on his agenda.
Stating that Dublin Airport would assume some €100 million in debt from Shannon and Cork, he presented the plan as an opportunity for the two airports to develop new business.
