Aer Lingus has confirmed that it has written to SIPTU warning that staff will be suspended if they do not cooperate in training new employees recruited on lower terms and conditions.
The move marks an escalation of industrial tension at the airline, where strike notice by SIPTU is due to expire on Wednesday.
Aer Lingus has recruited 12 new check-in and boarding staff on the new conditions which are part of the company's new cost-cutting plans.
The new members are receiving basic training from management, but from next Wednesday they are due to shadow-experienced staff on what are known as 'buddy days'.
However, last Friday, SIPTU notified management that they would not be cooperating with training these new recruits.
In today's letter to the union, management says assisting with the integration of new staff in any department is an integral part of the normal duties of all Aer Lingus employees.
He says the airline expects employees assigned to these responsibilities to fully cooperate with this requirement.
But he then warns that it is important that all employees understand that if they fail to carry out their full range of duties, for whatever reason, they will be suspended from the payroll with immediate effect.
SIPTU branch secretary Christy McQuillan confirmed that they had received the letter.
He said the contents were presently being considered by the union's clerical committee.
On Monday evening, their views will be brought to a meeting of the disputes committee.
He added that SIPTU will then decide the nature and timing of any industrial action.
EC deadline on Ryanair bid extended
The European Commission has extended the deadline for its examination of Ryanair's bid to buy Aer Lingus to 13 June.
It had been due to make a decision on the matter on 11 May.
A spokesman for the Commission said both sides had agreed it would be useful to have the extra time because it is a detailed and complicated case.
