Summary
We propose to adopt a new airworthiness directive (AD) for all The Boeing Company Model 737-300, -400, and -500 series airplanes. This proposed AD was prompted by a determination that supplemental inspections are required for timely detection of fatigue cracking for certain structural significant item (SSIs). This proposed AD would require revising the maintenance or inspection program, as applicable, to add supplemental inspections. This proposed AD would also require inspections to detect cracks in each SSI, and repair of any cracked structure. We are proposing this AD to address the unsafe condition on these products.