This Tuesday afternoon, staff Ryanair pilots based in Dublin, who are members of the Irish Airline Pilots' Association (IALPA) announced they would take industrial action over pay, plus terms and conditions of employment.
Impact said Ryanair was the only Irish-based airline that refused to recognise unions and the dispute was "solely about winning independent representation for pilots in the company".
Of the 84 ballots issued in Dublin, 79 voted in favour of industrial action, with three against, one vote spoilt and one not returned.
It is unclear at this stage what impact it will have on people travelling home for Christmas but most of the pilots balloted for strike action are captains, without whom planes can not fly.
Ryanair said it will deal with any such disruptions "if or when they arise" and said it wanted to "apologise sincerely" to passengers "for any upset or worry" the threatened action may cause.
Impact trade union official Ashley Connolly said: "This dispute is exclusively about winning independent representation for pilots in the company".
Impact official Ashley Connolly explained: "This dispute is exclusively about winning independent representation for pilots in the company".
In its statement, Cockpit claimed pilots were leaving the airline "in droves" for the better conditions offered by other carriers, leaving Ryanair with a shortage of aircrew.
The airline's statement also said it will not recognize the Aer Lingus pilot union, "no matter how often or how long this tiny minority try to disrupt our flights or our customers plans during Christmas week".
Ryanair said it would deal with any disruptions and expressed "surprise" the union had opted for action during the run-up to Christmas.
Irish-based pilots are holding the 24 hour stoppage just five days before Christmas, although there are reports that flights from Shannon won't be affected as pilots there have already agreed a new pay deal.
Ryanair boss Michael O'Leary urged pilots not to leave and promised better pay and working conditions.
Pilots and crew announced a series of plans across Europe.
IMPACT acknowledged that the move will either disrupt flights or generate substantial costs to the airline.
"This dispute is about securing a safe space for negotiations, with independent representation that pilots can have confidence in".
Members of the Irish Air Line Pilots' Association overwhelmingly backed the industrial action during secret ballots.
However, the union said that the 117 represent nearly 90% of pilots directly employed by Ryanair, and the majority are captains, a rank needed on every flight. If the action goes ahead, it will be the first time flight crew at Ryanair have ever walked out on strike.