Michael O'Leary, the combative boss of Ryanair, is challenging a European Commission ruling that the budget airline has been receiving illegal subsidies.
O'Leary says he has lodged a formal appeal with the European Court of First Instance against the EC ruling that the airline received illegal state aid from Charleroi airport in Belgium.
The airline says it is seeking to have the EC's "flawed decision" annulled arguing that the Commission "completely ignored" the fact that the carrier also has lower cost deals at some private airports.
O'Leary said the ruling had created a very damaging precedent for under-used regional airports in Europe.
He accused rival high fare airlines of using the ruling to undermine competition.
Ryanair had been ordered to return €3 million ($3.7m; £2m) to the Belgian authorities.
O'Leary argues the airline spent eight times more than that setting up the Charleroi operation in April 2001 and was justified in trying to offset some of the costs.
Data sourced from: Financial Times; additional content by WARC staff