The European Commission has opened a formal investigation into an agreement between Ryanair and Bratislava airport, which it says may breach state aid rules.
A complainant has alleged that the airport offers Ryanair reduced airport charges for existing destinations and new scheduled flights. The agreement was allegedly made in December 2005 for a period until 2016.
The reduction could be as high as a 31 per cent discount for existing destinations and a 48 per cent discount per flight for new scheduled destinations, the commission said.
"At this stage, in spite of its requests, the commission has not been provided with the text of the agreement."
The commission has requested that document as well as the necessary information to carry out its assessment pursuant to EU State aid rules.
"The commission's decision to investigate requires the airport to submit a copy of the agreement to it. So far the airport has refused to comply with this request. Without access to this document, and on the basis of the information provided by the complainant, the commission has doubts about its compatibility with EU rules on State aid."
In a statement, Ryanair claimed the European Commission was "biased" in applying "one set of rules for high-fare flag carriers and another set of discriminatory rules for Ryanair".
"The Commission's investigation is based on a spurious complaint [by a competitor] in order to block competition from Ryanair and Bratislava airport," Ryanair said, adding that the investigation was "completely baseless".
"While the Commission responds rapidly to these baseless complaints from Competitor airlines/ airports, it is doing nothing at all to investigate and address the serious multi billion euro state aid subsidies to flag carrier airlines (Air France, Alitalia, Lufthansa and Olympic)," Ryanair said.
"The European Commission's lack of action over these serious state aid cases, has now forced Ryanair to take separate cases against the Commission in the European Court of First Instance, to compel the Commission to apply its own state aid rules fairly and without discrimination against Ryanair."