Pilots at Emerald Airlines are set to hold a 24-hour work stoppage just ahead of the August bank holiday.
The pilots union IALPA has said its members will stop working on Friday August 4th.
It claims airline management has "ignored repeated requests to meet Fórsa and IALPA to negotiate a collective agreement" around pay, pensions and terms and conditions.
Emerald operates regional flights, including the public service obligation Dublin to Donegal service, on behalf of Aer Lingus.
In March the operator said it had carried over one million passengers in the past 12 months.
Fórsa Communications Officer Niall Shanahan told Breakfast Briefing members have already been taking part in a work-to-rule action.
"What has happened over the last several months is that Emerald Airlines management has simply refused to engage with union representatives, despite this being the express preference of the pilots who work at the airline," he said.
"We balloted the pilots in May and they voted overwhelmingly in favour of industrial action.
"What commenced in June was a work-to-rule action and that escalated this week.
"So for example, pilots are not being contactable out of their working hours, they won't accept a roster change if there's fewer than 24 hours notice.
"Yesterday they served notice on the airline of a one-day 24 hour stoppage, which takes place this day next week".
'Action of last resort'
Mr Shanahan said it was not their intention to target the August bank holiday weekend.
"Partly it's just the timing that we find ourselves in, this ballot took place back in May," he said.
"The initial work to rule action commenced in June, escalated in July and pilots made the decision to further escalate.
"It happens that we are right up against the August bank holiday weekend.
"This type of action is the action of last resort - nobody takes it lightly, but the pilots are genuinely left in a situation where they feel they have no other option.
"Unless we see meaningful engagement from Emerald Airlines management on this issue, the likelihood is that the action will continue and that it will escalate," he added.
Aer Lingus has been contacted for comment.