Airworthiness Directives; Boeing Model 737 Series Airplanes

This amendment supersedes an existing airworthiness directive (AD), applicable to certain Boeing Model 737 series airplanes, that currently requires repetitive inspections to detect cracking of the lower skin at the lower row of fasteners in the lap joints of the fuselage, and repair of any cracking detected. This amendment requires that the inspections be accomplished at more frequent intervals. This amendment also adds a requirement for modification of the fuselage lap joints at certain locations, which constitutes terminating action for repetitive inspections of modified areas. This amendment is prompted by reports of numerous fatigue cracks in the lower skin of the fuselage lap joints at the lower row of fasteners. The actions specified in this AD are intended to prevent such fatigue cracking, which could result in sudden decompression of the airplane.