WASHINGTON (AP) — Orders to U.S. factories for big-ticket manufactured goods jumped 11.2% in July, the third consecutive monthly gain.

And the jump last month was even larger than the 7.7% increase in June, the Commerce Department reported Wednesday.

The strong advance last month, however, was led by the volatile transportation sector, which spiked 35.6%. Excluding transportation, orders would have risen by a more modest 2.4%.

A closely watched category that serves as a proxy for business investment plans rose a solid 1.9% in July after a 4.3% rebound in June.

While the gains in orders for durable goods is welcome, economists caution that could falter if coronavirus infections surge in the fall, forcing more factory shutdowns and a return to the near economic stall the U.S. went through this past spring.

“The details of the report indicate that businesses remain wary as the initial post-lockdown burst in activity is winding down and the public health situation isn’t under control,” said Lydia Boussour, senior U.S. economist at Oxford Economics.

The big jump in transportation was led by a 21.9% surge in orders for motor vehicles and parts which offset another big decline in demand for commercial aircraft as airlines continue cancelling previous orders in the face of a plunge in air travel linked to the coronavirus.

The 11.2% rise in orders in July left total durable goods orders at a seasonally adjusted $230.7 billion.