Aer Lingus said its total passenger numbers - including those on its regional operations - fell by 0.1% in December to 733,000 from 734,000 the same time the previous year.
The airline said its short haul passenger numbers fell by 1.5% to 648,000 in December 2013 from 651,000, but its long haul passenger numbers jumped by 11.8% to 85,000 from 76,000.
Aer Lingus said its load factor - how many seats it fills on each flight - rose by 3 percentage points to 73.9%. Its short haul load factor rose by 1.7 points to 68.3% with capacity falling by 5.1%.
The airline's long haul load factor rose by 4.3 points to 82% as capacity on long haul routes rose by 4.9% on the same time the previous year.
Aer Lingus said it carried a total of 10.7 million passengers last year, including passengers on its regional operations which are operated by Aer Arann.