SIA Engineering has posted a 9.7 per cent drop in its third-quarter net profit from the same period a year ago to $60.5 million, due to a rise in expenses and a smaller exchange gain.

Revenue for the three months ended Dec 31 last year climbed 2 per cent from a year ago to $283.8 million, while expenditure grew at a higher rate of 4.7 per cent year-on-year to $258.6 million.

As a result, operating profit fell 19.2 per cent to $25.2 million.

"The increase in expenditure was mainly from staff costs, subcontract and material costs." the company said.

There was also a smaller exchange gain of $100,000 in the third quarter, as compared with a gain of $1.6 million in the same period the year before.

Basic earnings per share was 5.43 cents for the quarter.

Net asset value per share as at Dec 31 last year was 115.9 cents.

The near-term global economic outlook remains uncertain, SIA Engineering said.

"Rising business costs, particularly labour cost, present challenges to our operating environment. This will continue to put pressure on MRO [maintenance, repair and overhaul] yields."

The firm said it remains focused on managing costs by pursuing improvements in productivity and enhancing operating efficiencies. Overall, it added, its performance is expected to remain stable.