Ministers from five European governments warned the Irish low cost airline Ryanair on Friday that it could face legal trouble if it ignores national labour laws.
Employment ministers from Belgium, Germany, Italy, Luxembourg and the Netherlands urged the firm to resolve ongoing disputes with local employees within weeks.
Ryanair has run into trouble in several countries with staff based around the continent angered at being employed on contracts signed under Irish rules.
The European Commission has already warned Ryanair's chief executive Michael O'Leary that he must apply local regulations in each country in which he has employees.
Now national governments are adding their weight to the dispute, siding with labour unions and local regulators over the buccaneering Irish operator.
"Ryanair and its subcontractors are exposed to legal risks by not applying local labour law," the ministers said, in a letter addressed to O'Leary and seen by AFP.
The officials urged Ryanair to agree a timetable with unions to transition existing contracts with pilots and cabin crew to their local labour laws.
"We sincerely hope this materialises in the next few weeks," they said.
"For Ryanair there is now a window of opportunity for concluding an agreement with the trade unions which could become the basis for sustainable social peace."
In a statement, the firm insisted that it already follows EU-wide rules and was discussing how to address local disputes over national rules.
"Ryanair continues to negotiate with our people and their unions across Europe and we have already confirmed that we are offering local contracts and local laws," the firm said.
© 2018 AFP