Aer Lingus has said last month's closures due to the volcanic ash cloud would cut second-quarter earnings by about €20 million.
In an interim management statement, the airline said the final cost would depend on the level of customer claims, adding: "It is also uncertain whether the recent Icelandic volcanic eruptions will have a longer-term impact on passenger travel plans".
Aer Lingus, which has been cutting costs, said its first-quarter operating loss halved to €37.8 million, from €74.8 million reported the same time last year.
"While we are very encouraged by first quarter trading, it is nonetheless appropriate to remain cautious on full-year 2010 performance," it said.
Fuel costs fell 43 per cent to €54.9 million, the carrier said. The average fare for long-haul and short-haul flights rose 12.4 per cent and 3 per cent in the first quarter.
Aer Lingus shares rose 1.4 per cent to 74 cents on the Dublin market this morning. The stock has gained 16 per cent this year, boosting the carrier's market value to €395 million.