Airline passengers in the United States are getting bumped off flights more frequently than at any time in the past six years, the government reported yesterday.

Some 16,300 passengers were bumped against their wishes in the April-June quarter, a rate of 1.12 passengers per 10,000. That rate is one-third higher than a year earlier. The airlines' rate of what the Department of Transportation calls "involuntary denied boardings" was the highest since the same quarter in 2000.

In all, the DOT said, airlines bumped about 185,000 passengers during the last quarter, also up from the year-ago quarter. Most volunteered to give up their seats.

The worsening problem with bumping reflects the intensifying push by airlines to fill a greater percentage of seats. Grappling with soaring travel demand, continuing financial problems and record high fuel prices, airlines are filling planes fuller to maximize ticket revenue while holding down operating costs. No. 1 American Airlines filled a record 87 percent of its seats last month.

Southwest Airlines bumped nearly 32,000 passengers voluntarily or involuntarily in the quarter, more than any other airline. But the Dallas-based discount giant also carried more passengers than any of the 19 airlines covered in the DOT report.

According to the DOT report, the percentage of delayed and canceled flights also increased from a year earlier.

Summer 2006 is shaping up as the most troublesome for airline passengers in years, in part because of unexpected problems. During the week of July 16, New York City suffered a power outage, and Tropical Storm Beryl fouled up flights from New York to New England. On July 26 and 27, a Northwest Airlines computer glitch delayed more than 2,700 flights.