Shares in travel operator Thomas Cook plunged almost 20 percent Thursday after the British company revealed a drop in summer bookings, in particular to key market Turkey, following deadly attacks.
Around 30 minutes after the start of London trading, Thomas Cook was down 17.8 percent at 73.55 pence on the capital's second tier index.
Adding to the unease was news that an EgyptAir flight had vanished from radar screens Thursday en route from Paris to Cairo with 66 people on board. The airline said the cause of the disappearance was unknown.
Thomas Cook meanwhile said in an earnings update that demand for summer holidays in Turkey "remains significantly below last year", while summer booking across all destinations were down 5.0 percent year-on-year.
Excluding Turkey, summer booking were up 6.0 percent in the six months to March 31.
The group added that net losses during the first half of its financial year narrowed slightly to £269 million ($393 million, 350 million euros).
"Despite disruption in some of our key markets, we've managed to slightly grow our revenues... having anticipated the shift in demand away from Turkey, Tunisia and Egypt and into the Western Mediterranean and long haul destinations," chief executive Peter Fankhauser said in the earnings statement.
Turkey has experienced two deadly attacks in Istanbul this year blamed on Islamic State (IS) jihadists, and a pair of attacks in Ankara that were claimed by Kurdish militants.