As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING MAINTENANCE BASE VISIT FOUND THE COCKPIT UNDERFLOOR CENTER BAYS FROM FRAME 13--15 CORRODED. THE AIRCRAFT WAS REMOVED FROM SERVICE. REPAIRED COCKPIT UNDER FLOOR FRAME 13 TO FRAME 15 CORROSION IAW EO EM-53MR-1882. THE AIRCRAFT WAS RETURNED TO SERVICE.