U.S. factories reported an unexpected decline last month in new orders for long-lasting machinery and equipment, driven partly by a dearth of orders at the troubled aircraft maker Boeing (BA) - Get Report .

New orders for manufactured durable goods fell by 1.3% in May to $243.4 billion, the U.S. Census Bureau reported Wednesday in a statement. Economists, on average, had expected no change during the month, based on a survey by data provider FactSet.

The Census also said that the decline in orders in April was bigger than previously reported, down 2.8% from March levels. A month ago, the bureau had said that the orders slipped just 2.1% during April. 

The monthly durable-goods report is a key indicator of how busy factories will be in the future, and a slew of recent data have suggested that manufacturers are cutting back amid signs that the U.S. economy is slowing.

Some economists say that the troubles could be led by manufacturers, which are facing a slowdown as President Donald Trump's trade war with China drags on, driving up the cost of imported parts and raw materials while dimming prospects for U.S. sales. 

Economists typically caution that the figures can swing widely due to episodic orders of big items like aircraft from the likes of Boeing. 

Ian Sheperdson, chief U.S. economist at the forecaster Pantheon, had noted prior to Wednesday's release that Boeing, which has been plagued with negative headlines since the second fatal crash of its 737 MAX, reported no orders during May.  

The Census report reflected that drop-off, with new orders for non-defense aircraft and parts falling 28% from April levels, the biggest decline among categories tracked.

Excluding transportation equipment, new durable-goods orders rose 0.3%, slightly ahead of economists' projections for a 0.2% increase.

The increase was driven partly by a 1.7% increase in new orders for communications equipment.