Seattle ? The Boeing Co. plans to cut 4,000 to 5,000 more jobs than previously planned from its commercial airplane division by the end of the year, as the airline industry remains mired in the worst downturn in its history.

The cuts will come through attrition and layoffs, said Boeing Commercial Airplane chief executive Alan Mulally in an e-mail sent to employees. After the terrorist attacks of Sept. 11, 2001, Boeing had said it would need to cut 35,000 from its work force by the end of 2003.

At the company’s Wichita facility, the latest announcement is not expected to have any effect on the 5,000 jobs lost through layoffs and attrition there since the terrorist attacks, said Boeing-Wichita spokesman Fred Solis.

The Kansas plant is six months ahead of other commercial production at other Boeing facilities, meaning those reductions have already been made in Wichita, he said. Boeing has even called back some laid off workers. With its military business growing, workers have also been able to transfer to jobs on the military side of the company.

Now, with the continuing aviation slump, Chicago-based Boeing says it must further slash employment levels.

“This is an unprecedented and very difficult time for all of us in the commercial aviation business,” said Mulally, a Kansas University and Lawrence High School graduate. “While we are optimistic about the long-term outlook for the industry, many of our airline customers continue to face significant challenges as they struggle to recover their financial health and regain the ability to order new airplanes and related services. These actions are extremely painful for all of us at Boeing.”

By the end of the year, the commercial airplanes division work force will be 55,000 to 56,000 — about 60 percent of the 93,000 employed before the attacks.