Budget airline EasyJet PLC (LON:EZJ) warned that the outcome of the UK's EU referendum would hit second-half revenue.
The Luton-based carrier said it expected likely extra economic and consumer uncertainty this summer to reduce revenue per seat by at least a mid-single digit percentage, compared to the same period last year.
It said recent movements in fuel prices and exchange rates should add about £25mln of extra costs in the year compared to guidance given at the half-year.
EasyJet also said it had faced a tough May and June with 1,061 cancellations in the third quarter due to air traffic control strike disruption.
It also blamed runway and congestion issues at Gatwick airport, severe weather and knock-on cancellations across the easyJet network.
As a result, in June alone there had been more than 700 cancellations to date, with strikes and weather conditions making up most of these and more than flights cancelled in the last week.
That was up from 487 cancellations In June last year, of which 420 related to a fire at Fiumicino airport in Rome.
A spokesman said: "EasyJet's unique network, digital leadership, cost advantage and financial strength will ensure it continues to achieve its strategy."