Ryanair passenger traffic grew 6 per cent last month to 9.3 million as against 8.8 million for January 2017.
The airline said rolling annual traffic to January grew 9 per cent to 129 million customers.
Load factor rose 1 per cent to 91 per cent.
Ryanair agreed to recognise unions in December following strike threats from members of the Irish Airline Pilots’ Association (Ialpa) and equivalent groups in Germany, Italy and Portugal.
The carrier signed a union recognition deal with the British Airline Pilots’ Association (Balpa) earlier this week, the first of its kind since it reversed its policy on organised labour in December.