By John S. McClenahen Like the horizon in Kansas, 2003 is looking pretty flat to general aviation manufacturers. There simply won't be much change from 2002, a year that saw both shipments and billings of airplanes manufactured worldwide decrease about 15%. Total shipments of piston-powered planes, turboprops and business jets declined to 2,539 last year, 15.2% below the 2,994 shipments in 2001, says the Washington, D.C.-based General Aviation Manufacturers Association (GAMA). Total billings decreased to $11.9 billion in 2002, 14.4% under 2001's $13.9 billion. For planes manufactured in the U.S., shipments totaled 2,214 last year, down 15.9% from 2,634 in 2001. Billings were $7.8 billion in 2002, down 9.9% from $8.9 billion in 2001. "We have all established our production schedules, and they are likely to only slightly increase, even if the [U.S.] economy immediately starts to grow at a healthy rate," says W.W. Boisture Jr., GAMA's chairman and president of Gulfstream Aerospace Corp.