Boeing warns upcoming 787 deliveries may be delayed while it inspects the most recently built aircraft for wing cracks.

The inspections, which affect some 43 aircraft either awaiting delivery, in assembly or in early build, will take “one to two weeks” says Boeing. The issue concerns the appearance of hairline cracks “in a limited number of shear ties on a wing rib in the 787. This condition may be present in a limited number of airplanes still in production,” it adds.

Boeing says the problem emerged when it was notified by its Japanese wing supplier Mitsubishi Heavy Industries “that a change in their manufacturing process may have led to hairline cracks.” The manufacturer adds it is “confident that the condition does not exist in the in-service fleet. We understand the issue, what must be done to correct it, and are completing inspections of potentially affected airplanes. We are addressing affected airplanes as required.”

While it anticipates potential hold ups to some of the aircraft in the affected batch, some 25 of which are thought to have either already entered pre-delivery flight test checks or completed assembly, it expects no impact to 2014 delivery guidance.

The problem is thought to be focused on over-torquing of fasteners used to connect aluminum shear ties on the wing ribs to composite wing panels.