What was found
AIRCRAFT WAS AT FL 390 FOR 2 HOURS. WINDSHIELD DE-ICE WAS OPERATING. A SMALL AMOUNT OF ARCING ON THE COPILOT WINDSHIELD PROBES WAS OBSERVED. THE WINDSHIELD OUTER PANE CRACKED IN SEVERAL PLACES. THE COPILOT VIEW WAS NOT OBSCURED. PRESSURIZATION WAS NOT LOST. A DESCENT AND LANDING FOLLOWED WITH NO FURTHER PROBLEMS. PROBLEM OCCURRED ON SEPT 24, 1998. ACFT TT: 12,667 HOURS.