Low-cost airline Easyjet has said the disruption caused by the recent volcanic eruption in Iceland will cost it between £50m and £75m.
The cost means the airline has lowered its profit forecast for the full-year to between £100m and £150m.
The carrier reported a £78.7m loss for the six months to the end of March, against a £129.8m loss a year ago.
Meanwhile, TUI Travel said the ash disruption had cost it £90m, as it reported a six-month loss of £367m.
The deficit was worse than the £333m loss it recorded a year earlier, but Europe's biggest travel operator said the performance was in line with expectations.
As well as reporting smaller losses, Easyjet said revenue for the six-month period increased to £1.2bn from £1bn a year earlier.
Despite the disruption, Easyjet said it was on course to deliver "remarkable performance" this year.
"Easyjet will deliver substantial profit growth in 2010 through the worst recession in 70 years," said chief executive Andy Harrison.
The company also said it had increased its market share of short-haul flights over the past 12 months to 7.6%, up from 6.5% in the previous 12 months.
Easyjet said the disruption caused by the Eyjafjallajokull volcano last month forced it to cancel 6,512 flights, disrupting 850,000 passengers.
It said it was in the process of seeking compensation from governments for the additional cost and lost revenues incurred due to the five-day closure of European airspace.
The airline also said it had been hit to the tune of £21m by the "exceptional snowfall" in December 2009 and January 2010.