"Because we consider that there was unfair commercial practice, we denounced the situation to ANAC, which is not only the national implementing body with regard to compliance with community [European Union] regulations, but also has supervisory powers regarding unfair commercial practices," Deco legal officer Rosário Tereso said.

In addition, she told Lusa, "we shall contact Ryanair to express our concerns."

The complaint relates to the discovery by Deco that "already after the strike notice [was issued], Ryanair continued to sell tickets, concealing information that would be essential about that same strike notice," Tereso explained.

"Even on 17 July [Tuesday] Ryanair was still selling flights, only to later, the following day, proceed to cancel some of these and force passengers to request reimbursement for them and even to lose worthwhile opportunities to purchase tickets from other companies," she said. At the time it issued the tickets, she alleged, the carrier "would already know that there was a great likelihood of such flights not taking place and what was seen is that many of these flights were indeed cancelled.”

This conduct, in Deco’s view, “constitutes unfair commercial practice because the company omitted essential information to passengers, who could have managed to avoid a decision to purchase a ticket decision that they would not have taken if they had been informed in good time,” she stressed.

Trade unions representing cabin crew of the Ireland-based airline have called a strike for 25 and 26 July in Spain, Portugal and Belgium, and in Italy for 25 July.

They are demanding that Ryanair strictly observe local laws on employee rights in each country where it operates and recognise elected union representatives, who aim to negotiate a collective work agreement.

According to Deco, given the practice outlined, Ryanair will have to compensate any passengers that request this.

"In these cases where the company already knew in advance and nevertheless decided, at its own risk, to continue selling tickets, this situation does not represent an extraordinary situation under European regulations and so, in our view, the right to compensation is unquestionable,” said Tereso.

In addition, Deco is concerned about cases in which Ryanair did not provide the necessary information to passengers about flight cancellations.

In all, some 300 flights a day have already been cancelled for next Wednesday and Thursday as a result of the planned strikes. Up to 50 of the more than 180 Ryanair flights a day into and out of Portugal may be affected, according to the company.