Even before the July 14 attack, flight reservations to France were down by 16 percent for the two months compared to the same period in 2015 due to the Paris attacks in November, ForwardKeys said.
The Spanish-based company has access to databases of more than 200,000 online and physical travel agencies.
For Nice alone, air bookings from abroad have slumped 19 percent after the Bastille Day attack. They had already been projected to fall by 14 percent, ForwardKeys said in a statement.
"As an immediate reaction, international visitor arrivals in Nice dropped by 9.4 percent in the week after the attack, when compared with the same time last year," it said.
"Across the country, post-attack arrivals were down 8.8 percent.
