The Irish airline has seen passenger growth of 17% in 2015, after it adopted a new policy of being nicer to its customers.
The airline said that it had increased traffic by 50% for the month of December over the past two years.
Ryanair is returning to Belfast after an absence of five years. The airline is taking over slots from Belfast International Airport to Gatwick that were used by Aer Lingus.
Both of Belfast’s airports have been losing passengers to Dublin airport, since the Irish government scrapped air passenger duty.