Airworthiness Directives; The Boeing Company Airplanes

We are superseding Airworthiness Directive (AD) 2009-21-01 for certain The Boeing Company Model 737-300 and 737-400 series airplanes. AD 2009-21-01 required repetitive inspections to detect cracking of the aft fuselage skin, and related investigative and corrective actions if necessary. This new AD adds certain inspections, repairs, replacement, related investigative and corrective actions if necessary; and removes certain airplanes from the applicability. This AD was prompted by an evaluation by the design approval holder (DAH) indicating that the aft fuselage skin is subject to widespread fatigue damage (WFD), and by reports of aft fuselage cracking. We are issuing this AD to address the unsafe condition on these products.