Aer Lingus members of the Irish Airline Pilots’ Association (Ialpa) voted 99% in favour of action on a turnout of 89% following a fresh ballot at the weekend as part of an ongoing dispute with their employer over pay.

It comes after an electronic vote last week returned a 98% favourable result, although the validity of the ballot was questioned by Aer Lingus. Ialpa president, Captain Mark Tighe, said the second ballot – completed in-person – "reaffirmed" the union’s strike mandate with members seeking "a meaningful pay offer".

However, Tighe stressed action this summer was "not inevitable" despite the vote, telling the BBC it was his and Ialpa members’ hope that the result would relay the "strength of feeling" to Aer Lingus management.

He said the intervention by the carrier’s bosses, which resulted in the ballot being re-run, had only served to "further antagonise" its members. "They are now more determined than ever," he said.

The union must give at least a week’s notice of any plans to strike, and has confirmed Aer Lingus has approached it seeking 15 days’ notice, which would avoid it having to pay passengers cancellation compensation.

Aer Lingus is reportedly set to carry up to around 40,000 passengers a day this summer on its domestic routes, as well as routes to Europe, the US and Canada. While the action would be limited to pilots employed by Aer Lingus in Ireland, many UK travellers fly transatlantic with Aer Lingus via Dublin. It is thought up to 95% of services could be affected.

The carrier said it was continuing to engage in direct discussions with Ialpa and has requested the support of Ireland’s Workplace Relations Commission to explore further solutions, although this intervention has so far been rejected by Ialpa.

Aer Lingus Regional services in the UK, which are operated by Emerald Airlines, will not be affected should there be a strike.