Airworthiness Directives; Boeing Model 707 and 720 Series Airplanes

This amendment adopts a new airworthiness directive (AD), applicable to all Boeing Model 707 and 720 series airplanes, that requires repetitive inspections of certain stringers and around certain fastener holes of the lower skin of the wings to detect fatigue cracking, and repair, if necessary. This action is necessary to detect and correct such cracking and consequent damage to adjacent structure, which could result in reduced structural integrity of the airplane. This action is intended to address the identified unsafe condition.