Aer Lingus is threatening 1,100 compulsory redundancies if staff do not approve a €97m cost-cutting programme.
The staff are currently balloting on the measures which include staff cost reductions of about €74m and about 700 redundancies, along with pay cuts and pension changes.
Agreement was reached with pilots, cabin crew, ground staff and craft workers in recent weeks. It is understood, however, that management now fear staff may not accept the proposals.
Aer Lingus chief executive Christoph Mueller has briefed his management team to prepare 'Plan B' to secure the required cost savings through compulsory redundancies and a significant fleet reduction.
Aer Lingus originally set a target of 18 November to reach agreement on the cost-reduction package.
Meanwhile, the controversial Hangar 6 at Dublin Airport which was a the centre of a row between Ryanair and the Government, is to be used as a new centralised staff operations centre for Aer Lingus.
The hangar already houses the airline's maintenance division and has space for more than 400 staff in modern offices. It is planned to move 350 staff there by the middle of the year for a centralised operations centre with maintenance and technical stores, operations control, flight and cabin operations.
An Aer Lingus spokesperson explained that offices elsewhere on the airport campus, which are currently used by some of these, are coming to the end of their leases and the staff will be moved to Hangar 6.
The aim of centralising staff was to "create synergies".
The staff who will be moved to the hangar are from several different offices but not Aer Lingus headquarters The hangar can accommodate up to 400 office staff but at the moment there are only plans to move 350 to the facility.
It was recently at the centre of a storm when Aer Lingus refused to hand over the hangar to Ryanair for wide-aircraft maintenance. Tanaiste Mary Coughlan came under pressure from Ryanair boss Michael O'Leary who said he could create 300 jobs if and only if he was given a lease on Hangar 6.