The dual threats of terrorism and economic uncertainty have been blamed by Iata for a slowing in global airline passenger demand.
Year-on-year demand for flights rose by 5.2% in June from 4.8% the previous month.
However, the upward trend in seasonally-adjusted traffic has moderated since January, Iata reported.
June capacity increased by 5.6%, and the load factor slipped 0.3 percentage points to 80.7%.
Iata director general and chief executive, Tony Tyler said: “The demand for travel continues to increase, but at a slower pace.
“The fragile and uncertain economic backdrop, political shocks and a wave of terrorist attacks are all contributing to a softer demand environment.”
He added: “The latest figures show that aviation and aviation related tourism delivers $2.7 trillion in economic impact and supports some 62.7 million jobs worldwide. It is a powerful force for good in our world.
“It is too soon to know whether recent terrorist attacks will have a long-term negative influence on demand, nor what will be the impact of Brexit and the events in Turkey.
“But it is vital that governments recognise and support aviation’s ability to contribute to global economic well-being and better understanding across cultural and political borders.”
International Airlines Group reported a 6.1% rise in premium traffic in July.
Overall traffic was up by 15.7% over the same month last year for the owner of British Airways, Aer Lingus, Iberia and Vueling.