The number of passengers flying in the front of the plane on premium tickets fell 16.7 percent in January, a trade group said on Tuesday.

The International Air Transport Association estimated that with fewer passengers, revenue from first- and business-class travel probably fell at least 25 percent in January, "wreaking significant damage to network airline yields and profitability."

By January the economic downturn had spread to Asia, and premium travel numbers fell the most there - 23.4 percent fewer high-end passengers within Asia, and 24.7 percent fewer premium passengers flying across the Pacific. Premium travel to Europe fell 22.2 percent.

IATA said banking is a key sector for business travel, so the collapse of that sector hurt sales of premium tickets.

Economy travel has been falling more slowly, but that's probably in part because of coach-class travel for the Chinese New Year, which fell in January rather than February.

"The trend in travel overall is still downwards with, as yet, no bottom to the decline in sight," IATA wrote in the report.

Africa saw premium traffic grow, with 18.9 percent more passengers in January. Fares there also appeared to be holding up, IATA wrote.

Airlines generally have been flying less to try to match their capacity with lower demand. IATA said the Middle East was the only region where capacity grew, up 10.8 percent, mostly because of deliveries of new planes. "It remains a severe challenge to fill these seats in this recessionary environment," IATA wrote.