Thomas Cook said its summer bookings fell by 4% as the tour operator was hit by a slide in demand for holidays in Turkey following a series of terrorist attacks and an attempted coup.
The holiday giant has suffered after an ongoing spate of terror attacks from a variety of groups in Turkey, as well as a failed military coup in the country in July.
It added in a trading update that bookings were also "significantly down" in Belgium after the terrorist attacks at Brussels airport in March.
The holiday firm said that overall summer bookings are down by 4% across the group, although once Turkey is stripped out bookings are up by 8%. It added its summer programme is 89% sold so far.
Demand from British sun-seekers held up well over the summer, with bookings up 1%, but sales tumbled by 9% in Germany and across continental Europe.
Chief executive Peter Fankhauser insisted travellers still wanted to holiday overseas, but have switched to destinations such as the Balearic and Canary Islands and the United States, alongside smaller destinations like Bulgaria and Cuba.
Fankhauser said: "Customers' desire to go abroad on holiday has remained strong with the exception of Turkey where demand continues to be volatile."
The firm added that its summer and advanced winter bookings were in line with expectations, adding that its full-year guidance remained unchanged.
Analysts at Numis expect the firm to post an annual pre-tax profit of £165.7m, 6% down on a year ago.