MINNEAPOLIS — The number of passengers traveling on premium airline tickets dropped 1.5 percent in August, according to the International Air Transport Association.

"Business travel is a key driver of long-haul and network airline profitability, so the fall in volumes is a major concern for financial performance," IATA wrote in a report distributed recently. However, IATA noted that airlines worldwide have been raising fares, so revenue from premium tickets has still risen despite the drop in the number of passengers.

IATA said August was the third consecutive month in which the number of travelers on premium tickets shrank faster than the month before. But the number of passengers flying on premium tickets grew an average of 1.5 percent in the first half of the year.

Most premium ticket buyers are business travelers, and they are "highly sensitive to the economic cycle and to activity in key industries such as financial services," IATA wrote.

The number of passengers traveling on economy tickets fell 0.2 percent during August.

The weakness in premium travelers is concentrated in Asia or markets linked to Asia, IATA wrote. Still, some routes bucked the trend. North Atlantic premium and economy passenger numbers each grew 4.1 percent in August.