Ryanair will go to a Dutch court later to try to stop pilots in The Netherlands joining 24-hour strike action alongside colleagues in four other countries tomorrow.
The Dutch pilots announced last night they would walk off the job after their union said efforts to negotiate a collective labour agreement had failed.
Ryanair has now cancelled hundreds of flights with up to 25,000 passengers affected.
Employment law professor at Maynooth University, Michael Doherty, says the strikes could cause problems for the company's long-term business:
Mr Doherty said: "The danger for Ryanair is, while it may contain the numbers of passengers affected on Friday, people are thinking about booking October, Christmas and New Year trips and the question is are they confident now Ryanair will get them out of this?
"And, to be honest, there isn't a great sign of any movement forward in terms of resolutions from the company side."
