AlHijjah 17, 1433, Nov 2, 2012, SPA -- Demand for U.S. manufactured goods rose in September by the largest amount in 18 months, the government reported Friday, but a measure of business investment plans pointed to weak momentum in the economic recovery. The Commerce Department said factory orders rose 4.8 percent in September. The result, slightly higher than analyst expectations and the biggest gain since March 2011, reversed a 5.1 percent drop in orders in August. The September gain was driven by a surge in demand for commercial aircraft, a volatile category that had seen orders plunge in August. Aircraft orders rose more than 2,500 percent, following a 97 percent drop in August. Overall orders for transportation equipment jumped 31.3 percent in September. Excluding transportation, factory orders rose 1.4 percent. Orders for durable goods—expensive manufactured items expected to last at least three years—surged 9.8 percent, the biggest monthly gain in almost three years. Orders for primary metals rose 3.9 percent, orders for machinery gained 9.2 percent, and orders for non-durable goods—like chemicals and paper—rose 1 percent. Orders for non-defense capital goods excluding aircraft—a closely watched measure of business confidence and investment plans—showed a 0.2 percent gain in September and an upwardly revised 0.3 percent gain in August, but the tiny increases followed big declines of 5.6 percent in July and 2.7 percent in June. In the July-September period, business investment in equipment and computer software was flat, the weakest performance since the second quarter of 2009, when the country was in recession.