Boeing (BA) said Friday it will inspect the wings of about 40 Dreamliner jets still in production after learning of a possible manufacturing defect at a supplier.

According to the company, delivery of some 787s to airlines will be delayed as a result. Initial inspections revealed cracks in the wings of some undelivered Dreamliners.

Mitsubishi Heavy Industries, which makes the wings for Boeing’s jumbo jet, notified the aircraft giant that a change in its manufacturing process may have led to hairline cracks “in a limited number of shear ties on a wing rib in the 787,” Boeing explained in a statement.

A Boeing spokesperson said the company expects no impact to its delivery guidance for 2014. Boeing anticipates deliveries of 110 units this year.

The affected areas are very small and Boeing can fix each jet in one to two weeks, the spokesperson added.

“We are confident that the condition does not exist in the in-service fleet,” Boeing said. “We understand the issue, what must be done to correct it, and are completing inspections of potentially affected airplanes.”

The potential wing defect follows significant battery troubles for the 787, as well as a problem discovered in 2010 at an Italian company that was supplying horizontal tails.

Boeing was forced to redesign its Dreamliner battery pack last year after several high-profile malfunctions. Troubles related to the 787’s lithium-ion batteries grounded the fleet for several months in 2013.

Shares of Boeing fell 1% to $127.20 in after-hours trading Friday.

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