Cut price airline Ryanair says it appears to have lost a dispute over the state subsidies it is paid to fly to Charleroi airport in Belgium.
Ryanair expects the worst from the court ruling
A formal ruling is expected next week, but Ryanair says it will have to repay several million pounds in subsidies.
The airline also says the ruling will mean a ban on future subsidies, which will threaten many of its routes.
Ryanair manages to keep fares low by negotiating discounts at airports that want to attract more passengers.
It says that without those discounts, many of the routes would be uneconomical, and would have to be cut.
But the low-cost operator met the European Commission on Monday night and was told that the subsidies were illegal and would have to end.
Ryanair will also have to repay millions of dollars in marketing support it received from Brussels Charleroi airport.
Ryanair's boss, Michael O'Leary, says this is the worst possible result, and that he will appeal against the Commission's formal ruling when it is issued next Tuesday.