WASHINGTON — Orders to U.S. factories rose by a larger-than-expected amount in July as demand for commercial aircraft, heavy machinery and iron and steel all posted solid gains.

The Commerce Department reported Wednesday new orders increased by 1.3 percent in July, much stronger than the 0.8 percent increase economists had been expecting. The July advance follows an even bigger 2.1 percent increase in June and represents the fifth straight rise in orders.

Manufacturers have seen a sharp slowdown in the U.S. economy offset by strong gains in foreign demand, helped by a weaker dollar which makes their products more competitive overseas.

The July strength was led by a 28.1 percent jump in commercial aircraft, which rebounded from a 21.3 percent decline in this volatile category in the previous month.

Orders in all transportation categories rose by 3.2 percent in July, the best showing in five months.