The profit decline is the first since 2009 and in part reflects easyJet's exposure to the security-hit destinations of Egypt and Turkey and the French cities of Paris and Nice.

That combined with the devaluation of the pound since Britain voted to leave the EU in June mean that easyJet has fared worse this year than its bigger low-cost rival, Ireland's Ryanair.

Shares in easyJet dropped 6.4 percent to 938 pence by 0840 GMT, their lowest level since 2013. They are down 45 percent this year, the second worst performer on Britain's bluechip 100 index.

easyJet said pretax profit would be between 490 million pounds and 495 million pounds for the year to the end of September, below an already reduced analyst consensus forecast for 497 million pounds.

The airline had warned in July that uncertainty meant it could not give a profit forecast as it usually does at that time.

The weaker pound will result in a 90 million pound hit to profit in both 2015-16 and the new financial year after sterling fell to its lowest level against the dollar in three decades.

Chief Executive Carolyn McCall said that the carrier had been disproportionately affected by disruption this year and that she was confident in its future.

"The current environment is tough for all airlines, but history shows that at times like this the strongest airlines become stronger," she said.

easyJet's ticket prices fell 8.7 percent over the last three months and the company expects the trend to continue into the current quarter, suggesting intense competition in the European short-haul market driven by low-fuel prices showed no sign of letting up.

Ryanair said in September that fares could fall by between 10 and 12 percent over the six months between September and March.

Analysts at several brokerages said the combination of currency headwinds and lower fares would prompt them to cut their profit forecasts for the 2016/17 financial year by as much as 10 percent.

"Given the seasonality of easyJet and the airline industry, we see it as unlikely there will be a positive catalyst much before summer next year," said Liberum's Gerald Khoo, who rates the stock a "sell".

Cantor analyst Robin Byde argued that, like Ryanair, easyJet, was well placed to handle a competitive market, underlining their threat to the established carriers like British Airways, Lufthansa and Air France-KLM.

"For me, it's still mainly easyJet and Ryanair against the rest, and the low-cost carriers are frankly discounting quite aggressively at the moment to keep cabins full and to keep their growth plans on track," said the analyst, who has a "buy" recommendation on easyJet.

(Reporting by Sarah Young; editing by Kate Holton)

By Sarah Young