Wichita ? The Boeing Co.’s decision Wednesday to lay off 800 workers at its Wichita defense plant sent shudders through this aviation community, marking the third major layoff in a month at one of the city’s aircraft manufacturers.

While Boeing blamed the layoffs at its Integrated Defense Systems facility in Wichita on the delay of a U.S. Air Force tanker replacement program and the end of other work projects, the cuts come at a time when local business jet manufacturers are already struggling with the global financial credit crisis.

Hawker Beechcraft announced earlier this month it plans to lay off nearly 500 people, with Cessna just days later also saying it was laying off 500 workers in Wichita.

The city’s aviation sector has also been affected by the recently settled Machinists union strike against Boeing. Most of the 10,500 employees at Spirit Aerosystems — a major Boeing supplier of aircraft parts — are still working three-day weeks as Boeing gradually resumes commercial airplane production.

The layoffs announced Wednesday amount to 27 percent of the work force at Boeing’s Wichita IDS plant.

“It is one more impact to the economy here in Wichita and the surrounding communities,” said Bob Brewer, Midwest director for the Society of Professional Engineering Employees in Aerospace.

The cuts also come amid contract negotiations for the more than 700 Boeing engineers represented by the Wichita unit of the Society of Professional Engineering Employees in Aerospace. The announcement adds greater urgency to contract language that would have dealt with voluntary layoffs for workers who wanted to retire or move on from the company.