"It could be evidence of an easing in underlying economic conditions, which would be of concern to airlines and airports worldwide," CAPA said.
International air freight volumes are seen as a key forward indicator of global economic activity.
In August, Lufthansa Cargo transported 137,000 metric tons of freight and mail, down 3.5 pct year-on-year, as capacity grew faster than demand, putting further downward pressure on cargo load factors.
Lufthansa's cargo load factor was 60.4 pct in August against a year to date average of 64 pct.
IATA's July data continues a trend of falling international freight volume growth, which over the first six months of the year was just 3.4 pct compared with international passenger growth for the first half of 8.8 pct.
The organization sees the freight volume data as indicating extraordinarily high fuel prices are softening international trade.
IATA represents 265 airlines comprising 94 pct of international scheduled air traffic.
CAPA said Asia's biggest freight carrier, Korean Air, reported an 8.8 pct slump in freight volume in July from the previous July.
US airline industry organizaton Air Transport Association (ATA) reported that air freight volumes of its member airlines fell 1.7 pct in July, as measured by revenue ton miles (RTM), limiting growth for the year to date to 0.8 pct.
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