As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
MCN - DURING C-21 CHECK FOUND 2 CRACKS .275 INCHES IN LENGTH. BOTH CRACKS LOCATED ON THE BOTTOM OF THE NR 4 SLAT SKIN, AT SS 72 TO SS 74. MAINTENANCE CUT OUT DAMAGED AREA AT NR 4 SLAT SKIN AND FABRICATED REPAIR DOUBLER AND FILLER IAW BOEING 737-300 SRM 57-43-01. INSTALLED REPAIR PARTS IAW BOEING 737-300 SRM 51-40-02.