As many as 20% of Aer Lingus flights will be cancelled next week in the first five days of a work to rule by pilots.
The cancellations from June 26 would enable the airline “to protect as many services as possible for as many of our customers as possible”.
Details of the cancellations will be communicated to impacted passengers “over the next couple of days”.
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People due to travel between June 26 and July 2 will be given the option to change their flights for free.
They will also be able to cancel their flight and claim a refund or voucher.
“These options will be communicated directly to impacted customers as well as travel agents,” Aer Lingus said.
The airline made the announcement after the Irish Airline Pilots Association (Ialpa) served notice of an indefinite work to rule on Tuesday as part of an ongoing pay dispute.
Aer Lingus has said that transatlantic flights from Manchester airport and regional services operated by Emerald Airlines would be unaffected by the industrial action.
However, the airline said: “The work to rule announced is an insidious form of industrial action which will have a cumulative and negative impact on Aer Lingus customers.
“Its indefinite form is designed to severely disrupt passengers in the peak of the summer season. The impact will cause many flight cancellations – many of which may happen close to the time of travel.
“Therefore, in order to protect as many services as possible from the impact of the industrial action, Aer Lingus has to take the step of cancelling between 10% and 20% of our flights on the first five days of the industrial action.
“These cancellations will be implemented over the course of the next two days. Implementing these cancellations is to enable us to protect as many services as possible for as many of our customers as possible.”
Aer Lingus added: “Ialpa’s industrial action will have a wholly unnecessary impact on customers who are travelling in the coming weeks, at what is peak holiday season for families.
“The nature of this industrial action will cause a significant impact on our flight schedules. However, our focus is on minimising the impact on customers and communicating directly with those who are affected, including, notifying them of the options that are being made available to them.
“We will also be communicating directly with third party agents including travel agents and online agents. Passengers who booked through a third-party should contact their sales agents for any updates.
“We will do everything we can to minimise the impact for customers. However, it is inevitable that there will be disruption as a result of this industrial action, and we will communicate any changes, delays or cancellations to impacted customers as soon as possible.
“Where there are cancellations, we will look to reaccommodate customers as quickly as possible and will work with other airlines, with partner airlines and seek to hire-in aircraft for this purpose.”