Vegard Einan, from Norway's Parat union, said that a case launched on Monday by a Belgian union on behalf of six workers showed ex-Ryanair staff were no longer scared to battle their former employer.
"I think the floodgates are now open," he said. "We have been contacted by cabin crew from Germany, from Holland, and from Spain, who have all asked for our help to get into contact with their national unions. So I would expect more of these case to be held in the future."
Ryanair has until 16 September to appeal last month's decision by a Norwegian court that Alessandra Cocca, an Italian air hostess stationed in Norway, should be eligible to sue Ryanair for unfair dismissal in Norway, rather than in Ireland, where Ryanair claims she was employed.
The former flight attendant, who compared her work agreement to a "slave contract", claims she was wrongly dismissed from her job while stationed at Rygge Airport in Norway.
Ryanair spokesman Robin Kiely, said the company would send the "bizarre" decision to appeal in Norway's Supreme Court.
Norwegian law, he argued, should not apply to work done “outside Norway, by an Italian citizen employed on an Irish contract by an Irish company subject to Irish law and who paid her taxes and fees in Ireland."
Einan said he too hoped that their appeal was successful.
"We really want it to go to the Supreme Court," "because this is a situation which has never been tried in Europe. This is the first time this has been tried in aviation, because aviation is a highly mobile business."
He said Ryanair's business model rested on avoiding the higher tax rates and more generous employment rights its competitors were forced to give employees in countries like Norway, by claiming that all of its staff are stationed in Ireland.
"It's more convenient and profitable for them if they can use Irish taxes and work contracts all over Europe," Einan said.
"Even if Norwegian Airlines and SAS were to have their employees work for free, the tax costs and employment costs would be higher than Ryanair pays today."
He said that Ryanair staff had up until now been deterred from complaining by the threatening clauses in their contracts.
"This is the first case in Europe where one of the employees of Ryanair dares to stand up against the company. That's because of the culture of threats that exists in Ryanair. The contracts are full of clauses saying if you tell journalists what it's like to work for Ryanair, we will sue you."