US airlines may bump the most passengers in nine years as business travelers resume flying following the deepest cuts in seats since World War II.

Almost 220,000 passengers couldn’t get on flights in the first quarter even though they bought tickets, 25 percent more than a year earlier, US Transportation Department data show. At that pace, so-called denied boardings in 2010 would surpass 2009’s 762,400 and reach the highest total since 2001.

“It’s more than inconvenience,” said Kevin Mitchell, chairman of the Business Travel Coalition, which represents about 300 corporate travel buyers. “There’s the risk of lost sales opportunities and lost productivity.”

The increase stems from a traffic revival at carriers led by Delta Air Lines Inc. and AMR Corp.’s American Airlines, which haven’t yet restored reductions in capacity made during the recession. Continental Airlines Inc. and Southwest Airlines Co. said their planes flew fuller than ever in May.

Pent-up demand for summer vacations means there won’t be many empty seats in the coming months, probably resulting in more bumping, said Rick Seaney, chief executive officer of Dallas-based ticket-research firm FareCompare.com.

Airlines routinely sell more coach tickets than they have available, betting that not all passengers will show up. “Unless there’s a new law or something, it’s not going to change,” said George Hamlin, president of Hamlin Transportation Consultants in Fairfax, Virginia.

About 89 percent of first-quarter bumpings were voluntary, with travelers accepting inducements such as vouchers to switch flights. (Bloomberg)