May 24 - Citing sluggish sales in a withering economy, Cessna Aircraft Company laid off 30 percent of its workforce today at the Independence, Kansas, facility where it makes piston-engine airplanes. Cessna cut 280 of the 1,000 jobs at the factory. "It's something we certainly didn't want to do," said Cessna spokeswoman Marilyn Richwine. Cessna was planning to build 1,100 airplanes this year but is now shooting for 900. Cessna noted a drop in sales after the first of the year as potential buyers became more sensitive about discretionary spending, she said. But the turbine market remains strong for both the Citation and Caravan lines.