What was found
DURING FLIGHT, AT FLIGHT LEVEL, 21,000 FT, COPILOTS WINDSHIELD INNER PANEL CRACKED. PILOT IMMEDIATELY DESCENDED TO A SAFE ALTITUDE AND LANDED AS SOON AS POSSIBLE. UPON INSPECTION, FOUND NO DAMAGE TO OUTER PANEL. WINDSHIELD HEAT WAS OPERATING NORMALLY. NO REASON FOUND OR DETECTED FOR FAILURE.