EasyJet (LON:EZJ) tempered a record first half performance with a caution that the current quarter will be more difficult.
The early Easter break and disruptions due to French Air Traffic Control strikes mean third quarter revenue per seat will likely fall by four percentage points, said chief executive Carolyn McCall.
The airline produced a rare profit in the first half of the year thanks to a lower fuel price and an exchange rate gain.
Pre-tax profits came in at £7mln in the six months to 31 March, traditionally the much weaker period for airlines, compared to a £53mln loss in the same period in 2014.
Exchange gains were £18mln while fuel costs were £20mln lower.
“As expected the lower oil price has been beneficial for customers and easyJet will be able to offer its customers even better value fares this summer while continuing to grow revenue and profit” the company said.
EasyJet is the UK's largest short-haul airline with a 20% market share. Capacity rose by 3% in the six months.
McCall said a strong finish to the ski season boosted the interims as well as fuel.
The growth in the European short-haul market looks set to continue in the second half of the year as a result of improved economic conditions and a lower oil price, the company said.
It had also increased the number of seats on its A320 aircraft, which makes up more than a third of its fleet, from 180 to 186 through a redesign of the aircraft cabin.
Shares dropped 7% to 1,702p in early trading.