Cirrus Design has reacted to slumping sales by lowering its production rate to three aircraft per day from four per day. The Duluth, Minnesota, manufacturer also expects to cut back to a three-day week for at least some of the remainder of this year, though Cirrus would re-up the per-day rate to four under that schedule. They will continue to build 12 airplanes per week. Production of Cirrus SR22 and SR20 piston singles is down some 10 percent; not as bad as the average for the rest of the piston fleet-where deliveries are down 16 percent over the first half of the year, according to figures from the General Aviation Manufacturers Association. Last month, Cirrus cut its staff by 100, and announced last week it intends to retard development of its light sport model, initially expected to be certified next year. Development of the Cirrus Vision SJ50 single-engine jet, however, remains a high-priority project, with orders received for more than 400. Company president Alan Klapmeier hopes an economic incentive package passed by Congress will boost sales for the fourth quarter of this year. Buyers can accelerate the depreciation of aircraft bought this year, which affords significant tax benefit.