Airworthiness Directives; The Boeing Company Airplanes

We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 707 airplanes and Model 720 and 720B series airplanes. This AD was prompted by a determination that undetected web fatigue cracking caused by oil canning may exist in the aft pressure bulkhead web. This AD requires repetitive detailed inspections for any oil canning or cracking of the aft pressure bulkhead web, and corrective actions if necessary. We are issuing this AD to address the unsafe condition on these products.