Taxpayers may be propping up almost a quarter of European Union airports served by Ryanair, including Derry, Kerry and Knock, a report from lobby group Transport & Environment claims.
Brussels allows member states to subsidise regional airports, including those in the Republic and Northern Ireland, but is planning to review the guidelines governing this.
A report published by lobby group Transport & Environment, called Analysis of State Aid to Selected Ryanair Airports, estimates that "almost a quarter" of the EU airports served by the airline are likely to be loss making and propped up by taxpayers' money.
The group wants the EU to ban state aid for loss-making airports as it says this subsidises aviation’s high levels of greenhouse gas emissions and benefits shareholders in companies such as Ryanair.
Transport & Environment’s report states that its analysis found that of the 214 EU airports that Ryanair serves, at least 35, or 16 per cent, are likely to have received government subsidies, while a further 17, or 8 per cent, are likely to be losing money as they attract low numbers of passengers.
The report names Kerry and Knock airports in the Republic, and Derry in Northern Ireland, as being among those that receive state aid.
Last month, the Minister for Transport, Shane Ross, announced that the Government would give €5.7 million to Knock Airport and €2.2 million to Kerry Airport this year to spend on bolstering safety and security.
Transport & Environment says its analysis is not exhaustive. The group suggests that further research could show that local governments support other airports used by Ryanair, including Charleroi, an sizeable base used by the carrier in Belgium that handles about eight million passengers a year.
The environmental group points out that it is difficult to get figures on the aid that EU member states give to airports as their governments give little detail on this.
It took several steps to identify airports likely to be receiving aid including “an examination of passenger numbers and discovery of circumstances where airports were shown to be in receipt of public money”.
Transport & Environment took all airports that attract fewer than 500,000 passengers a year as likely to be loss-making and therefore potentially receiving subsidies.
The group said it singled out Ryanair as recent figures named the airline as a top 10 greenhouse gas emitter under Europe’s emissions trading scheme.
However, Ryanair says it has the lowest greenhouse gas emissions of any European airline.
Last month, its carbon dioxide emissions were 66 grams per passenger per kilometre, which it said was about half that of other carriers. Ryanair did not respond to a request for comment.