Ryanair and hundreds of thousands of its customers across Europe have been warned to brace themselves for “the biggest strike action the company has ever seen” which could happen before the end of the month.

Dutch, Spanish, Italian, Belgian and Portuguese representatives of pilots, cabin crew and ground handling workers issued a joint statement yesterday afternoon in which they said no real progress had been made on their demands since a pan-European strike over the summer.

The statement emerged after seven unions from the five countries held, what they described as, an “historic” meeting in Rome. There are suggestions they may ask their fellow Ryanair unions in their countries to join with them in the action.

The representatives claimed deals which have been achieved between unions and the company in different European countries are “far from consensual”, and that some would soon be subject to a legal challenge.

The union bodies also claimed the current executive board of directors at the company had demonstrated that they were “incapable of having meaningful talks with unions”.

“On September 20, the shareholders will have the opportunity to place Ryanair on the right track and ensure a long and sustainable model more suitable to the Europe of the 21st century by capturing the right talents to bring Ryanair to the level that we all want to see it,” the representatives said.

“If the company leadership is not willing to make the changes necessary, (the workers) will have no choice but to respond with the biggest strike action the company has ever seen.”

They said the strike will take place in the last week of September and will be announced no later than next Thursday.

A significant issue is that workers are employed under Irish law and so are not governed by local laws, with attendant rights and benefits, and they are to raise that with the European Commission.

Irish staff members were not represented at the meeting but Irish passengers would be significantly impacted by widespread action across Europe.

Fórsa only signed an agreement with the airline last week making it the sole negotiating union for cabin crew in Ireland. Pilots here have signed off on a new seniority agreement with the airline. Following that deal, the company confirmed, as expected, its board had decided to restore six Dublin-based aircraft which were due to transfer to Poland in November for the winter 2018 schedule.

It said the related protective notices issued to 300 Dublin pilots and cabin crew in July at the height of strikes by Irish pilots had also been withdrawn. The airline said the decision was taken in light of the deal signed with pilots.

“The board and management of Ryanair are committed to union recognition, and working constructively with our people and their unions to address their reasonable concerns, as long as this does not alter Ryanair’s low-cost model or our ability to offer low fares to our customers,” said the airline’s chief people officer Eddie Wilson, possibly in reference to the wider strike threat in Europe.

“Since December last year, when the board announced that we would recognise unions, Ryanair’s people have enjoyed significant pay increases, improved terms and conditions, and we have agreed to improved seniority structures, base transfers and annual leave.”