DEL LOCATIONS - INSPECTION AND MODIFICATION. SERVICE BULLETIN AND AN EXTERNAL NON DESTRUCTIVE INSPECTION (NDI) OF THE FUSELAGE SKIN FOR CRACKING AT THE CHEM-MILL STEPS COMMON TO SHEAR WRINKLE AREAS FOR ALL AIRPLANES. GROUP 2.5-6 MOS 28-MAY-2013 21-OCT-2011 -(s) 3714:04 AFL 900 SB 737-53-1311 TABLE 3.1 NON