A number of Ryanair flights out of Dublin have been cancelled.
IALPA pilots are holding their second 24-hour strike in just over a week.
Some 24 flights out of the capital to the UK have been cancelled today.
The company says it is cancelling flights on routes with higher volumes so people can more easily transfer to other services.
The 100 Irish-based staff already walked off the job last Thursday in their row over seniority.
The pilots, who are members of the Irish Airline Pilots Association (IALPA), are in dispute with the company over base transfers, leave and seniority issues.
Talks between their union and Ryanair management broke down earlier this week.
With no breakthrough in sight, more strike action is scheduled for next Tuesday.