Aer Lingus has confirmed it is to cancel 120 flights scheduled for next weekend due to a pilots’ eight-hour strike happening on June 29.

A spokesperson for the airline said it will impact 15,000 customers on short-haul services.

A previously announced, indefinite work-to-rule from June 26 – which would mean pilots would not engage in overtime or out-of-hours duties – saw the airline cancel 124 flights.

Aer Lingus said this will affect about 20,000 customers over the five days from the Wednesday as it pledged to accommodate people amid the busy summer holiday season.

A strike was announced by the pilots’ union for June 29, running from 5am to 1pm.

“Following Ialpa’s escalation of the industrial action by announcing an eight-hour strike by pilots on Saturday June 29, Aer Lingus has had to cancel 120 flights on that day,” an airline spokesperson said.

“This will impact 15,000 customers on Aer Lingus short-haul services. Aer Lingus has retimed long-haul services on both June 28 and 29 in order to avoid cancellation of these services.

“Aer Lingus is automatically rebooking some customers onto alternative flights and has begun emailing all other customers informing them of the cancellations and advising them of their options, to change their flight for free, to request a refund or to request a voucher.

“The detail of the cancelled flights on June 29 is available on the ‘Travel Advisory’ on the Aer Lingus website at aerlingus.com.

“Aer Lingus Regional flights, operated by Emerald Airlines, are unaffected by Ialpa’s industrial action and will operate as scheduled. Aer Lingus Regional flight numbers are in the range EI3000 – EI3999.”

The Irish Air Line Pilots’ Association (Ialpa), which represents the pilots, said it had been “forced” to escalate the dispute following “a campaign of antagonism by Aer Lingus management”.

The president of Ialpa, captain Mark Tighe, claimed the airline had sent “threatening” letters to association members.

“The scale of next week’s anticipated flight cancellations, as described by Aer Lingus, illustrates the extent to which the company relies on the flexibility and goodwill of pilots,” he said.

Aer Lingus condemned the planned strike action and said it was “appalled” that Ialpa would escalate the dispute, which it said was “clearly designed to inflict maximum damage on passengers’ travel plans”.

Ialpa is seeking a pay increase of 24%, which it says equates to inflation since the last pay rise in 2019.

Aer Lingus has described the pay demand as unrealistic and said there have been no pay deals in Ireland that delivered such an increase.

Om Friday, Irish premier Simon Harris said people need to “step back from the brink” in relation to the dispute.