The European Commission is suing France for failing to recover nearly €10m (£7m; $11m) in illegal state aid to two budget airlines.
Most of that amount is owed by the Irish airline Ryanair and its marketing subsidiary AMS, the Commission says.
Ryanair and Dutch carrier Transavia had rebates and marketing deals at three airports – Pau, Nimes and Angouleme.
The carriers therefore paid less than they should have for using the airports, the Commission says.
Ryanair profits have surged recently.
Net profits for the three months to June were €245m, up from €197m a year earlier.
The airline no longer flies to Pau or Angouleme.
A year ago, the Commission says, it told France to recover nearly €10m from Ryanair and Transavia. The case of Transavia concerned only €430,000 due for a deal at Pau airport.
France failed to meet a four-month recovery deadline, because the airlines appealed against the move.
But the Commission says France’s suspension of efforts to recover the funds contradicted European case law. It is now taking the case to the European Court of Justice.
In a separate case last October, a French court told Ryanair to pay €8.1m in damages and €200,000 in fines for breaches of French labour laws.
An appeal court in Aix-en-Provence found the company guilty of paying workers under Irish contracts to avoid making French social security payments.
The case referred to Ryanair staff employed at Marseille airport between 2007 and 2010.