Washington (AFP) - US manufacturing orders fell for a second straight month in September as aircraft orders continued to slip, the Commerce Department reported Tuesday.

New orders for manufactured goods dropped $2.8 billion, or 0.6 percent, to $499.4 billion. That followed a 10 percent downturn in August, with a fall in orders for Boeing aircraft, normally volatile month to month, mainly explaining the drop.

But manufactured goods shipments showed some strength, rising 0.1 percent in September to $503.4 billion.

Significant gains in new orders came in iron and steel mill output, likely driven by auto orders, and in power generation equipment.

But analysts said that the overall dull data, along with disappointing US trade numbers for September released earlier Tuesday, was likely to lead to the government lowering its third-quarter growth estimate.

The initial estimate last week put the pace of expansion during the July-September period at a surprisingly strong 3.5 percent annual pace.

Analysts at Barclays Bank on Tuesday lowered their tracking estimate for the quarter to 3.0 percent annual growth based on the new data.