We are adopting a new airworthiness directive (AD) for the products listed above. This AD results from mandatory continuing airworthiness information (MCAI) issued by an aviation authority of another country to identify and correct an unsafe condition on an aviation product. The MCAI describes the unsafe condition as the discovery of exfoliation corrosion in the fittings of some PC-6 airplanes. These fittings are installed exterior to the bottom skin of the wing skin. If not corrected, undetected corrosion in this area could lead to failure of the fitting and subsequent loss of control of the airplane. We are issuing this AD to require actions to correct the unsafe condition on these products.