Demand for long-lasting goods produced by U.S. factories decreased in May for the third time in four months, underscoring a broader slowdown in the manufacturing sector.

Overall orders for durable goods, manufactured products intended to last at least three years, fell 1.3% in May from the prior month, the Commerce Department said Wednesday. The decline was much steeper than economists surveyed by The Wall Street Journal had expected.

Much of the drop owed to the volatile civilian-aircraft component, which dropped 28.2% from April following a decision by global aviation authorities in March to ground BoeingCo.’s 737 MAX airliner after a pair of fatal crashes.

When excluding the transportation category, which tends to be volatile, orders grew at a 0.3% pace.

Excluding defense, another choppy category, durable orders decreased 0.6%, the third drop in four months.

An underlying business-investment gauge, new orders for nondefense capital goods excluding aircraft, increased 0.4% from April. Part of the rise in capital spending could reflect payback from April, when companies pulled back sharply on investment.