Aer Lingus said it carried a total of 782,000 passengers in March, a fall of 6.3% from the same time last year.
Its long-haul passenger numbers slumped by 20.7% to 69,000 last month while its short-haul passenger numbers also fell by 4.7% to 713,000.
The airline said its load factor - or how many seats it manages to fill on each flight - crept 0.3 points higher to 75.9% as capacity fell by 11.3%.
Its short-haul load factor eased by 2.7 points to 75.9% with capacity rising by 1.2%. Its long-haul load factor rose by 4.2 points to 75.7% with capacity decreasing by 29%.
Aer Lingus also noted that total passengers in March on its new Washington Dulles-Madrid codeshare flight with United Airlines were 1,669. This represented a load factor or 89.3%, it added.
