Aer Lingus's RPK passenger traffic grew 1.7% year-on-year in January.
The carrier's ASK capacity fell 2% during the reporting month, while its load factor rose by 2.3 percentage points to 64.6%.
Its short-haul business - excluding Aer Lingus Regional - saw year-on-year traffic decline by 4.2%, but the long-haul business climbed by 13.5%.
Load factor for short-haul rose by 0.2 percentage points to 62.7%, while long-haul recorded a 6.4 percentage point increase to 68.2%.
Passenger numbers at Aer Lingus Regional, operated by affiliate Aer Arann, grew 22.6% to 65,000.
Total passenger numbers across the group grew by 3.6% to 638,000 during January.