Boeing Co has revealed recently that "hairline cracks" were discovered in the wings of about 40 of its 787 Dreamliners that are currently in production, which may raise concerns for shareholders.

The company confirmed on Friday, March 7, that the cracks on the 787 Dreamliners have not been found on the planes that are already in use by airlines and, therefore, safe. Boeing also added that the current problem will not affect the company's plans to deliver 110 787 Dreamliners in 2014.

Boeing indicates that the cracks on the 787 Dreamliners occurred in shear ties on wing ribs, which run parallel to the fuselage of the aircraft. It will take the company one to two weeks to inspect and fix the problem.

Boeing also revealed that the cracks, which also occurred on the 787-9 model (currently undergoing flight tests), may be delayed by a few weeks.

Industry experts suggest that the latest manufacturing defect have raised questions about repair costs and a possible slight increase in the plane's weight. However, the issue does not seem to have caused major trouble for Boeing.

Apparently, in February this year, wing-maker Mitsubishi Heavy Industries Ltd alerted Boeing regarding the problem, which started after the Japanese company altered its manufacturing process. A spokesman for Mitsubishi Heavy Industries says that it is in discussion with Mitsubishi on how to deal with the situation.

Boeing suggests that it has already informed customers of a potential delay, which may arise because of the defect. The plane manufacturer also said that none of the jets potentially affected by the problem has been delivered and remain confident that the defect does not exist in the in-service planes.

The U.S. regulator, the Federal Aviation Administration (FAA) said that it is aware of the situation and will work with Boeing to ensure that the recent problems with the 787 Dreamliners are corrected before they are delivered to customers.

Boeing has been going through a rough patch as the company came under the regulator's scanner in 2013 also. The lithium-ion batteries overheated on two of the Boeing Dreamliners, which prompted regulators to ground the worldwide fleet for over three months.

Even though Boeing may be able to resolve the latest problem, it will have to incur an expense to arrange for a fix. The news related to the manufacturing defect on 787 Dreamliners has had an adverse effect on the Boeing's stock as shares fell 54 cents, or 0.4 percent, to $128.00 in after-hours trading on Friday, March 7.