Cabin crew at Aer Lingus are stepping up their action today in a row over rosters.
A work to rule has been underway at the airline for a week now.
However IMPACT, the union which represents cabin crew, says from today staff should strictly adhere to "on-call" rules, as stated in their contracts.
Members have also been told not to take phonecalls or respond to text messages from Aer Lingus on days off or during rest periods.
Aer Lingus says it does not expect the work to rule to cause disruption to passengers.