GENEVA — The world’s airlines saw strong growth in May for both domestic and international traffic, according to the International Air Transport Association (IATA).

Total revenue passenger kilometres (RPKs) rose 6.9%, which was an improvement on the April year-over-year increase of 5.7%. May capacity (available seat kilometres or ASKs) increased by 6.5%, and load factor rose 0.3 percentage points to 79.3%.

“May results confirm that demand for connectivity remains robust, but there are possible storm clouds forming on the horizon. The financial crisis in Greece and recent weakness in regional trade activity in Asia-Pacific have the potential to dampen performance in these markets in the coming months,” said Tony Tyler, IATA’s Director General and CEO.

North American airlines’ traffic rose 2.0% compared to May a year ago, which was an improvement on the April rise of 0.7%. Capacity climbed 4.2% and load factor fell 1.7 percentage points to 81.1%. Expectations for better economic performance in Q2 should support demand for air travel, but the strengthening dollar likely will continue to place downward pressure on international leisure travel to the U.S.