The airline says it has cancelled 30 of its 290 scheduled high frequency flights between Ireland and the United Kingdom, rather than hitting European routes used for family holidays to summer resorts.
It was also announced last week that cabin crews in Portugal, Italy, Spain and Belgium were also set to strike in solidarity with their colleagues.
Ryanair has confirmed that it is to cancel up to 30 flights to and from Ireland on Thursday.
"We will do this by cancelling a number of flights on high frequency routes from Ireland to London and other United Kingdom destinations where customers can transfer readily to other flights on Thursday or switch their travel to earlier flights tomorrow (Wednesday) or later on Friday, Saturday or subsequent days".
The airline has said only flights between Ireland and the United Kingdom will be affected.
It said it would also help customers travelling to the United Kingdom with alternative flights and ferries.
Passengers who have not received an email or text alerting them to the disruption can safely assume that their flight will depart as normal tomorrow.
Ryanair says it has contacted the pilots' union to ask them to cancel the "unnecessary" strike. However, its parent union Fórsa has said the strike is still likely to go ahead.
"Ryanair pilots have already secured a 20pc pay increase, earn up to €200,000 per year, work five days-on followed by four days-off, enjoy rapid promotions and unmatched job security", it said.
"We can not rule out further disruptions in July and August, especially when some Aer Lingus pilots wrote officially to the DAA on 25 June - some 10 days before the results of the Ryanair pilot ballot were known - to advise that they were "contemplating a series of 1 and 2 days strikes in July and August", it read.
The pilots have called the strike after talks with the budget airline broke down.
The airline has said it "cannot rule out further disruptions in July and August".