Ryanair was always going to have to recognise trade unions at some stage but the process was accelerated by the "mess up" over rostering last autumn, the airline has said.
Ryanair chief people officer Eddie Wilson said the company's decision late last year to negotiate with trade unions would add about €100 million to its costs on a full-year basis.
His comments came as the airline confirmed it had signed a union recognition agreement with the Italian Airline Pilots Association (Anpac), which will now be the sole representative body for Ryanair-employed pilots in Italy.
Speaking at the annual Industrial Relations News conference in Dublin, Mr Wilson indicated that the decision to recognise unions stemmed ultimately from the growth of the airline across Europe.
"We are the largest airline in Italy. We are the largest airline in Spain. For many years we were able to say we are just a small Paddy airline, making our way in the world with people still on Irish contracts of employment.
"What happened was the idea of running a recognition dispute in somewhere like Ireland or the UK is completely understandable, no matter what side of the fence you are on.
“In Spain or Italy it is not. There is a cultural difference. And it was a tipping point for us.”
Mr Wilson said Ryanair had always said it was going to recognise unions at some stage.
“Whether or not we were ever going to do it voluntarily, I don’t know. But I went to investor conferences every year and we always said that, particularly in the southern European markets, that we were going to do it some day.”
He said in locations such as Italy and Spain the airline had people on Irish contracts of employment “but gradually we were being boxed into a corner in terms of regulatory changes at European level”.
“It was going to come but we helped it along by messing up the rosters last year.”
Mr Wilson said Ryanair had now exchanged documents regarding recognition with the trade union Forsa (formerly Impact, CPSU and PSEU) in Ireland.
He said an upside for the airline of its decision to recognise trade unions was that it could now open up in France and Scandinavia and that it already had had contacts with French and Danish unions.
Mr Wilson indicated that one of its red lines in dealing with unions would be to ensure that “inefficiencies in legacy airlines” were not imported into Ryanair.
He said that would kill its business model.
Mr Wilson also told the conference that agencies which provide cabin crew to Ryanair on a contract basis had indicated that they would also recognise trade unions.