Aer Lingus has said it is operating on the basis of a full schedule over the weekend despite the ongoing cabin crew dispute.
The airline has hired aircraft from Ryanair and other airlines in an effort to operate a full flight schedule.
The company is to write to all cabin crew asking them to sign an undertaking to comply with the new rosters. If the workers do not comply, they will be sacked.
Trade union IMPACT, which represents the cabin crew, says management are "misjudging the mood" of staff by issuing threats to sack them.