NEW YORK (AFP) - Boeing said on Friday that hairline cracks have been found in the wings of some of its 787 Dreamliners still in production due to a manufacturing problem.

Boeing told AFP the cracks were found in the wings made by Mitsubishi Heavy Industries of Japan, but insisted it was "confident that the condition does not exist in the in-service fleet." Boeing said had been notified by its wing-maker supplier MHI that "a change in their manufacturing process may have led to hairline cracks in a limited number of shear ties on a wing rib in the 787."

The cracks may be present in a limited number of airplanes still in production, the Chicago-based aerospace giant said.

Boeing said it was completing inspections of the roughly 40 airplanes that are potentially affected. Deliveries may be delayed because of inspection and repairs, but the company expected no impact to its overall delivery expectations this year.

It was the latest in a series of problems that have beset the high-tech 787, including a months-long global grounding over battery problems last year.