Global air passenger traffic in April showed the slowest pace of growth since January 2015 as a result of the fatal bomb attacks at Brussels airport on March 22.
The demand, measured in total revenue passenger kilometres (RPKs), rose by 4.6% in April against a 4.9% increase in capacity (in terms of available seat kilometres or ASKs), while load factor slipped 0.3 percentage points to 79.1%.
The International Air Transport Association (IATA) singled out the Brussels attacks, which closed the airport for two weeks, as the main drag on the April figures, which had been projected to grow by 5% prior to the incident.
IATA director-general Tony Tyler said the disruption was likely to be short-lived but warned there were some longer-term clouds looming over the pace of demand growth.
"The stimulus from lower oil prices appears to be tapering off and the global economic situation is subdued. Demand is still growing, but we may be shifting down a gear," he said.
International passenger traffic, which accounted for 63% of overall global traffic volume, in April rose 4.8% year-on-year, the slowest pace in two years.
Demand for domestic travel climbed 4.1% in April compared with the previous year, while capacity increased 3.8%, causing load factor to rise 0.3 percentage points to 81.4%.
Airlines in all regions recorded growth in international traffic, led by the Middle East.
Total capacity climbed 5.6%, causing load factor to slip 0.6 percentage points to 77.8%.
Asia-Pacific airlines' April international traffic increased 6.4% year-on-year.
Slower economic growth in many regions has been at least partly offset by an increase in direct airport connections that has helped to stimulate demand.
Capacity rose 6.8% and load factor dipped 0.3 percentage points to 77.3%.
European carriers saw demand rise just 1.8% in April, which was considerably down from the 6% growth rate recorded in March -- directly reflecting the effects of the Brussels terror attacks.
Capacity for European airlines climbed 2.4% and load factor slipped 0.5% percentage points to 80.2%, which was still the highest among the regions.
Middle Eastern carriers posted a 12.7% traffic increase in April, the only region to see a double-digit percentage increase in demand.
Capacity growth of 14.8%, however, outstripped this rise.