A source speaking on behalf of the combined chambers of Limerick, Galway, Ennis and Shannon said lawyers retained by the campaign will give an opinion on whether a legal challenge to the decision is feasible this week, but have expressed optimism that a case could be made.

Campaigners say management was required to notify shareholders of its plans for the Heathrow slots before making any final determinations. Aer Lingus's articles of association allow a shareholder in control of more than 20% of ordinary shares to call an extraordinary general meeting if a disposal of Heathrow slots is proposed. According to statements in the Dail in April by then transport minister Martin Cullen, the government retained a 25.1% share in the airline precisely to activate that provision.

In a statement within the articles of association, Cullen also said Heathrow had a "unique role in ensuring connectivity to/from Ireland" and that the Shannon flights were "critical".

"On this basis, the Minister for Finance as a shareholder in the company, acting on the advice of the Minister for Transport, is unlikely to support a proposed disposal of any slot pair such that there would be less than the existing London Heathrow slot pairs that relate to services between London Heathrow and Cork or Shannon and is likely to request the convening of an extraordinary general meeting, as provided for in the Articles of Association, to consider such a matter."

The Department of Transport declined to comment on Friday.