Aer Lingus is warning that time to reach a deal to avert travel chaos next week is running out.
Talks between airline management and the IALPA pilots union have resumed at the Labour Relations Commission in Dublin.
Pilots are threatening industrial action on Tuesday over a rostering row which could result in significant disruption to around 30,000 Aer Lingus passengers.
Aer Lingus director of Human Resources, Michael Grealy, said there is still a lot of work to do and that concerned customers can now alter their bookings.
Mr Grealy said: "We are very concerned. We have a situation with our passengers where next week is looking increasingly serious.
"We have taken steps this afternoon to allow people who have bookings on Tuesday to cancel or change on the web for free. We would encourage our passengers to avail of that service where they think it is prudent."