Belgium is taking Ryanair to court.
The country's Deputy Prime Minister Kris Peeters has accused the airline of a lack of professionalism over the cancellation of thousands of flights.
The crisis caused by a mismanagement of pilots' leave has affected approximately half a million passengers, and is set to continue into next spring.
Mr Peeters says they are taking the action because Ryanair only communicated with Belgium's French and Dutch-speaking customers in English and a failed to notify them of their rights.
Ryanair said: "Ryanair complies fully with all EU261 legislation and is taking all necessary steps to re-accommodate affected customers."