Ryanair carried 9.5 million passengers last month, up from 1.9 million year-on-year but down on the 10.2 million carried in November.
The load factor at the low-cost carrier was 81 per cent, an improvement on the figure of 73 per cent seen during December 2020.
However, it was a fall on the load factor of 86 per cent seen in November last year.
Last month, Ryanair lowered its forecast for its expected December traffic from between ten-11 million to nine-9.5 million.
This was due to travel restrictions imposed amid the rise of the Omicron variant of Covid-19.
The low-cost carrier also said its net annual loss would be within the range of €250-€450 million – worse than the previous expected range of €100-€200 million.
Furthermore, the carrier cut its January capacity, which will see traffic fall from about ten million to between six million and seven million passengers this month.