Ryanair has confirmed that 24 flights between Ireland and the UK will be cancelled on Friday 20 July due to strike action by pilots.
A quarter of Ryanair's Irish-based pilots are taking industrial action over conditions.
Ryanair said that passengers on the flights have already been notified by text or email of the cancellations.
It said those flying with Ryanair on Friday who have not been contacted should expect their flight to go ahead.
Passengers who have had flights cancelled are being offered refunds or free transfers to alternative flights on different days, the company said.
On Thursday 12 July, Ryanair cancelled 30 flights between Ireland and the UK, due to a 24-hour strike.
A further day of strike action is due to take place on Tuesday 24 July.
The pilots' concerns include a dispute over seniority, as well as the procedures for allocation of base transfers, promotions and annual leave.
"This second strike is unnecessary because Ryanair has already given them [the pilots] written proposals that address their concerns about seniority - even though [pilots' union] FORSA and the pilots committee don't even understand that their demands will damage Irish pilots' prospects," a Ryanair spokesperson said.
"We've offered to set up a working committee to explain all these issues to this small minority and asked them to postpone this strike, but they have refused."
A union spokesperson said they had invited management to talks on Wednesday or Thursday and are awaiting a response.
The spokesperson said that current Ryanair proposals are not enough to resolve the issue but said their members remain committed to getting a resolution.
They added that the striking pilots are those directly employed by Ryanair with 99% of the 120 balloted voting for industrial action.
Ryanair has more than 250 self-employed pilots which allows the airline to operate most of its routes during the strikes.