The Forsa trade union, which had called for such mediation, welcomed Ryanair's response and said it would recommend it to pilots.

Europe's biggest airline by passenger numbers agreed to recognise unions for the first time late last year but negotiations since have faltered.

It has seen strikes in some of its biggest markets including Ireland, Spain and Italy as it struggles to reach collective labour agreements with trade unions.

Around a quarter of Ryanair's 350 pilots based in Ireland have taken part in a series of one-day strikes and a number picketed in the rain outside Dublin airport on Friday morning.

Ryanair has limited the damage from the Irish strikes so far and said passengers on the 20 flights it cancelled from the 300 that flew in and out of Ireland on Friday were either put on another flight or refunded.

However it faces greater disruption next Friday with Irish pilots joining colleagues in Sweden and Belgium on strike, and Ryanair braced for action in Germany and the Netherlands on the same day.

So far that has forced Ryanair to cancel 6 percent of the more than 2,400 flights it has scheduled across Europe next Friday - a further 20 to and from Ireland, 22 in and out of Sweden and 104 in Belgium.

Ryanair shares were down 0.2 percent at 12.98 euros by 1455 GMT, near two-year lows and well below the level hit in December when it shocked the markets by ending 32 years of refusing to recognise unions.

While the Irish airline has signed recognition deals in some markets, it has failed to do so in others and not yet reached any collective labour agreements.

"This is part and parcel of life in aviation when you recognise unions," Ryanair Chief Marketing Officer Kenny Jacobs told Ireland's Newstalk radio station, pointing to years of wrangling over pay and conditions at rival Lufthansa.

"There is going to be disruption, it will be small, we will manage it... We are making progress around the rest of Europe, strikes can be part of that process, they are not helpful, but we will get collective labour agreements in place over the autumn in our key markets."

(Reporting by Padraic Halpin; Editing by Jason Neely/Keith Weir)

By Padraic Halpin