Airlines have struggled to fill seats - especially the profitable ones at the front of the plane, and last-minute business travelers who pay more. Demand for business and first-class seats has dropped 20 percent, compared with a 5 percent drop in coach. The amount passengers will pay to travel is expected to fall 12 percent this year.

"When yields fall, they almost never recover," said Giovanni Bisignani, IATA's director general and CEO, speaking at a news conference in Washington.

Because of the recession, airlines are losing more money in 2008-2009 than they lost in 2001-2002 after the Sept. 11 attacks, Bisignani said. After Sept. 11, it took more than three years for airline revenues to recover