Ryanair, the no-frills Irish airline, said yesterday it was likely to be asked to pay back millions of euros of state aid it has received to fly to the Belgian airport of Charleroi.
Separately, EU officials said that the low-cost carrier would have to get used to operating its routes without government subsidies.
The Charleroi ruling, expected from Brussels early next week, is set to have major repercussions for the Irish airline and the way it operates. About 20 per cent of its flights are into airports where state authorities provide financial aid of one kind or another.
Speaking ahead of the publication today of Ryanair's third-quarter results, its head of regulatory affairs Jim Callaghan said that the fine that the Commission was likely to impose was "going to be in the millions". However, he added that Ryanair would immediately appeal if the decision went against it.
Belgium's Walloon government only charges Ryanair €1 per passenger to land at Charleroi. In 2002 it further subsidised Ryanair with €3.8m of support for fare promotion. But Mr Callaghan claimed the support Ryanair received was not very much different from that which it got from private airports.
In the past Ryanair's chief executive, Michael O'Leary, has suggested that one way around the state aid ruling would be for the Walloon region to privatise Charleroi, in which case Ryanair would offer to take a small minority stake as a sign of support.
Ryanair shares closed down 3.57 per cent in Dublin, with analysts citing nervousness ahead of the European verdict.
"Nobody likes uncertainty," said Shane Matthews, an airline analyst at NCB Stockbrokers.