Aer Lingus's long-haul traffic grew by 12.6% in March, contributing to an overall 4% rise in RPK traffic across the entire business.
Year-on-year traffic at its short-haul division - excluding Aer Lingus Regional - fell by 1%.
The carrier's ASK capacity fell 1.4% during the reporting month, while its load factor rose by 4.1 percentage points to 79.9%.
Load factor for short-haul rose by 4.7 percentage points to 77.3%, while long-haul recorded a 2.4 percentage point increase to 84.4%.
Passenger numbers at Aer Lingus Regional, operated by affiliate Aer Arann, grew 19.2% to 87,000.
Total passenger numbers across the group grew by 4.3% to 844,000 for the month.