Ryanair carried 9.5 million passengers in December – slightly down on November’s figure of 10.2 million.
The carrier operated more than 62,000 flights in the final month of 2021 with a load factor of 81 per cent.
The 9.5 million figure was down from a previous expectation of traffic of between 10 million and 11 million because of travel restrictions imposed by France, Germany and Morocco.
Ryanair announced in late December that it was lowering its full-year guidance to a net loss of between €250 million and €450 million because of the Omicron variant and government travel restrictions.
The airline also said at the time that the “sudden downturn” meant it had slashed its January capacity by a third.
Ryanair had previously stated a range of between €100 million and €200 million for the full year ended 31 March, 2022
The full-year traffic guidance was adjusted to just under 100 million passengers compared with the previous expectation of just over 100 million.
The airline said it hoped to provide more clarity later in January when it announces its third quarter results.