As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
LEFT FORWARD COCKPIT WINDOW CRACKED IN CRUISE AT FL 310 LARGE CRACKING PATTERN WITH SOME RESIDUAL VISION. AIRCRAFT TURNED BACK AND LANDED AT ORD. WITH OUT FURTHER INCIDENT. AIRCRAFT WAS GROUNDED BY MAINTENANCE. MAINTENANCE REMOVED AND REPLACED L1 WINDOW IAW B767 AMM 56-11-01. REMOVED AND REPLACED WINDOW HEAT CONTROLLER IAW AMM 30-41-01. AIRCRAFT RETURNED TO SERVICE