Pilots in the Netherlands have confirmed that they will join colleagues in Ireland, Belgium and Sweden for a 24-hour stoppage.
So far, Ryanair has scrapped 146 flights due to the strike. Up to 3,500 passengers will be hit in Ireland, where the budget carrier has already cancelled a number of flights.
Another 104 flights to and from Belgium will be grounded and 22 in Sweden. And the tally is set to rise if pilots in Germany and the Netherlands make a decision to join in.
Ryanair has refused to pay compensation to travellers, which is worth €250 per person for UK flights, because it claims the strikes are an extraordinary circumstance.
However, the Commission for Aviation Regulation has encouraged passengers to claim it even if they received refunds or were accommodated on other flights. If Ryanair turns down their request, they can appeal the decision to the regulator.
The British Airline Pilots’ Association says it cannot take part in the strike because of the requirements of UK industrial relations law on ballots and notice.