The National Consumer Agency (NCA) is planning a legal challenge aimed at forcing airlines to pay refunds to customers and display their prices more clearly.
The newly-created agency is also examining "unexplained differences" in the amount some airlines charge passengers for airport taxes and the amount they actually pass on to the airports, The Irish Timesunderstands.
It wants the airlines to list ticket prices inclusive of all taxes and charges, and to allow customers to opt in to charges for baggage, booking, check-in and insurance, rather than having to opt out of these costs.
NCA deputy director John Shine confirmed that airline consumer protection issues were "firmly on the agenda" but declined to comment further.
Research by the agency into the airline industry, including price transparency, possible unfair terms and misleading advertising has just been completed. It now plans to write to Aer Lingus, Ryanair and Aer Arann within weeks demanding changes to their terms and conditions, according to sources.
Having taken legal advice and consulted with the Office of Fair Trading (OFT) in the UK, the agency believes it has a strong legal case against the airlines under existing consumer legislation and under new powers conferred on it under the Consumer Protection Act. Investigators, having examined the airlines' websites, believe they have identified six areas where unfair terms are being applied.
The airlines are to be asked why they do not give full or partial refunds for unused tickets, and why the taxes and charges they collect on behalf of airports are not refunded if a passenger does not fly. Some operators are imposing a higher airport charge on passengers than they actually have to pay on to Dublin Airport Authority, which is capped at €6.34 per passenger, it is claimed.
Ryanair and Aer Lingus are already under pressure from the OFT to include all fixed, non-optional charges in the advertised prices of flights. Of 13 airlines written to by the OFT, the two Irish airlines are the last to comply.
As of last July, six months after the deadline, they were still citing technical problems with their websites for not having made all the changes required by the UK authorities.
The EU Commission has done its own research into the marketing practices of airlines in 15 member states, which will be published shortly. Although Ireland did not take part in the study, Aer Lingus and Ryanair are expected to feature prominently in the results.