AER LINGUS recorded a significant 15.9pc drop in passenger numbers within the last year.
The group said that overall capacity was down 13.6pc compared to November 2009.
The fall in figures comes amid reports of a drop in air travel tax expected in the Budget.
Minister for Finance, Brian Lenihan was expected to announce that the much-criticised tax could drop from €10 to €2 in today's cost-cutting Budget.
Aer Lingus, controlled by Christoph Mueller, said it had significantly reduced its long-haul capacity at the end of 2009 and made a similar reduction to short-haul capacity earlier this year in order to remove loss-making routes.
"These changes were made to achieve a better match between capacity and market demand in the core market of Ireland, and to remove loss-making routes," the group said in a statement.
"As a result, total November 2010 capacity was 13.6pc lower than last year."
The airline's load factor, or how many seats it fills on each flight rose by 1.3 percentage points to 72.3pc in November.
Long-haul load factor at the former flag carrier increased by 0.8 points to 71.9pc, with capacity falling by 0.4pc.
Its short-haul load factor increased by 1.6 points to 72.6pc with capacity falling by 20.6pc.