Aer Lingus pilots have overwhelmingly backed industrial action in an 'indicative' ballot over rostering.
Sources revealed that over 90pc of the airline's Irish Air Line Pilots' Association (Ialpa) members indicated that they were prepared to go on strike.
A confidential Ialpa note sent to the pilots said the indicative ballot for industrial action was carried out as a result of issues relating to rostering, crew control and "general under resourcing" at the airline.
It is understood that talks are under way in a bid to resolve the dispute.
Indicative ballots are carried out by unions to gauge whether there is an appetite for industrial action among their members, but do not have legal standing.
The Iapla note said negotiators met senior Aer Lingus managers late last month to highlight frustration about constant under crewing and issues relating to negotiations on a crewing agreement.
The note referred to recurring crew control problems and daily calls and texts to pilots to operate on free days.
It said the negotiators clarified that a Pilots Pay Tribunal can make any finding it likes, and nothing in a potential new agreement will affect that.
The note said the union hoped to be in a position to sign off on the wording of this new crewing agreement in the near future.
It said the agreement would then be put to a vote by members of the union.
An Aer Lingus spokesperson said it has had a lengthy and constructive process of engagement with the pilot group at the airline.
“In the last few days a comprehensive crewing agreement has been finalised and Ialpa has communicated positively to its members regarding this progress,” said the airline in a statement.
“As such, Aer Lingus can confirm that it has not been notified of any planned industrial action and based on having reached recent agreements does not expect to be there to be any risk of notice of such action in the foreseeable future.”