AECOM shares tumbled 5.53% in after-hours trading on Monday after the infrastructure consulting firm reported mixed fiscal third-quarter results, with a surprise operating loss overshadowing a significant revenue beat.

The company posted third-quarter revenue of $3.59 billion, far exceeding the IBES consensus estimate of $2.02 billion. However, AECOM disclosed an operating loss of $75.98 million for the quarter, a sharp downturn that rattled investors and triggered the after-hours selloff.

The stark contrast between the top-line strength and the operating loss raised concerns about the company's profitability and cost management, leading traders to quickly reprice the stock in the extended session.