The union representing Ryanair cabin crew in Belgium has rejected an offer from the Irish airline ahead of a planned one-day strike across five countries on Sept. 28, the union said on Wednesday.

Separately, European pilots threatened new strikes against Ryanair if talks with unions did not progress more quickly.

The company's shares have fallen around 9 percent this year, but gained about 1 percent on Wednesday, a day before shareholders were set to meet at the annual general meeting.

Europe's biggest budget airline offered to follow Belgian employment law from March 2020 for Ryanair contracted employees, seeking to address one of the major complaints over the company's policy toward staff under Irish contracts.

However, the Belgian union, CNE, said that would only help about half of its workers, as Ryanair had also been hiring using recruiter Crewlink, which issues its own contracts.

The union said the offer was an "unacceptable" attempt to divide workers in order to buy time ahead of the planned strike.

"It's a deception on the part of Ryanair," CNE spokesman Yves Lambot told Reuters.

The threatened strike by cabin crew in Belgium, Italy, the Netherlands, Portugal and Spain is aimed at pressuring shareholders set to meet on Thursday to address Ryanair's labor agreements, union officials announced last week.

The 24-hour strike is planned for Sept. 28 and unions will strike once a month until their demands are met.

The Belgian union met Ryanair officials before announcing the strike and received an offer on Tuesday evening, Lambot said.

Ryanair stood by its statement last week that, even if there is a strike, it expects a significant majority of its cabin crew in the five countries to work normally, as they have during previous strikes.

The British Airline Pilots Association said on Wednesday that it expected industrial unrest at Ryanair across Europe to continue for the foreseeable future.

"The industrial unrest in Ryanair across Europe and among pilots and cabin crew is, in my opinion, likely to continue for the foreseeable future," BALPA General Secretary Brian Strutton said in a statement.

The German pilots' union Vereinigung Cockpit (VC) also issued a similar statement.

BALPA called on Ryanair shareholders to replace CEO Michael O'Leary and Chairman David Bonderman at the company's annual shareholder meeting on Thursday.

The statement echoed the European Cockpit Association, which represents pilots in Europe, and also called on Wednesday for shareholders to pave the way for a change in the management and board of the airline, saying industrial unrest was more likely in the future.

Separately, Swedish Ryanair pilots urged shareholders to "immediately replace the current leadership and management at your annual general meeting."

"We have lost all confidence in the current leadership and management and their ability to guide the company in a unionized environment," the statement said.

A senior Ryanair executive said on Tuesday that CEO Michael O'Leary would continue at the company's helm for at least five more years.

In another setback for the airline, a Spanish judge has ruled a former Ryanair pilot should have been considered an employee and not an independent contractor.