Ryanair revealed a 22% fall in profits after it was impacted by rising fuel costs and "unnecessary" disruption caused by Iceland's volcano.
The low-cost airline booked exceptional costs of 50 million euros (£42.4 million) after the closure of European airspace forced the cancellation of 9,400 Ryanair flights in April and May and the loss of 1.5 million passengers.
After initially refusing to compensate customers beyond a refund for their ticket, Ryanair subsequently agreed to cover the costs of refreshments and accommodation for passengers who could not get home.
It said on Tuesday it was still processing claims under the "unfair and disproportionate" EU regulations, adding that it will be some time before the exact cost of the cancellations is known.
The estimate of 50 million euros meant pre-tax profits for the company's first quarter to June 30 fell to 104.6 million euros (£88.7 million) from 134.6 million euros a year earlier.
Fuel costs rose by 34% to 287 million euros (£243.3 million) due to higher oil prices and the introduction of new routes.
It is due to open its 42nd and 43rd new bases in Barcelona and Valencia in September and November respectively and said it continued to see "enormous opportunities" to grow the business across Europe.
However, it recently announced that it will cut winter capacity in the UK by 16%, including a 17% reduction in its services at Stansted airport in Essex, where the carrier will handle 1.5 million fewer passengers than last winter.
Ryanair chief executive Michael O'Leary cited the "damaging" Air Passenger Duty airport departure tax as a reason for the capacity reduction.
And while sticking by forecasts for full-year profits, he said the airline remained cautious about prospects for the rest of the year.