Ryanair has confirmed that it will recognise the British Airline Pilots' Association (Balpa) as the representative of all the airline's 600 pilots based in the UK.
The move marks a milestone for the Irish budget carrier, which has steadfastly refused to recognise unions in Britain before now. It has been under no legal obligation to recognise them.
The Irish carrier revealed in December that it was prepared to recognise pilot unions in some of its European bases as it sought to avoid strikes that could have wrecked its Christmas schedule.
Michael O'Leary, the airline's chief executive, said that decision had been taken to ensure that flights over the festive period would go ahead as planned after pilots in the UK, Germany, Italy, Spain and Portugal had threatened walkouts.
Eddie Wilson, Ryanair's chief people office, said that the agreement with Balpa, which was announced on Tuesday (30 January), highlighted the airline's commitment to working with the union to preserve pilots' and customers' interests.
"This agreement validates the decision of Ryanair's board in December to recognise unions," he said in a statement.
"[It] shows how serious Ryanair is about working constructively with unions that are willing to work constructively with us.
"Today's agreement between Ryanair and Balpa shows that Ryanair can work with unions that wish to work with us to promote the interests of both our pilots and our customers."
Brian Strutton, the union's general secretary, said: "I want to pay tribute to the Ryanair pilots who have themselves brought about this change in attitude from Ryanair management.
"I also want to thank Ryanair management for their professional attitude throughout this short process.
"While we were initially sceptical about Ryanair's sincerity in offering recognition to us and other unions, our conversations and meetings with them have shown that they are genuine in wanting a constructive trade union relationship."
In September, the Dublin-based airline was forced to cancel approximately 20,000 winter flights because of staffing problems. Some 700,000 passengers were affected.
The issue stemmed from its decision to reschedule its staff holiday year to run from January to December. That left to big gaps in the pilots' roster.
The blunder cost the airline €25m (£22m) in compensation costs and forced it to hike pilots' salaries. The airline claims they are now 20% higher than those offered by its rival Norwegian.
The new wage structure, however, will result in a €100m increase in costs this year for the airline, which has recruited 900 pilots so far this year.