Seven trade unions representing Ryanair cabin crews in five countries have threatened the airline with ‘the biggest strike the airline has ever seen.’

Unions representing cabin crew from Italy, Portugal, Belgium, Spain and the Netherlands met in Rome this afternoon.

The unions said they will strike at the end of the month unless Ryanair agrees to major changes to its working conditions.

The unions will release details of when the strike will take place by September 13th.

A representative of Portugal's SNPVAC union told the Reuters news agency that unions will invite pilots and ground staff to join the action.

Two Italian unions, two Spanish, and one each from Portugal, Belgium and the Netherlands are behind the strike.

Reports in Portugal indicate that the unions will also call for an urgent meeting of the European Commission and talks with EC President Jean-Claude Juncker.

Unions are calling for Ryanair employment contracts to be subject to the labour laws of the country in which the employees are working.

They are calling for “local law, local contracts and local standards” and have accused the airline of ignoring European and national labour laws.