As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ORD FLT 1623 DURING CRUISE AT FL340, EN ROUTE FROM CLT TO MSP, THE CAPTAIN'S L1 WINDSHIELD OUTER PANE CRACKED. PRESSURIZATION HELD OK. WINDOW HEAT WAS TURNED OFF AND NO FURTHER CRACKING WAS NOTED. FLIGHT DIVERTED TO ORD AND LANDED WITHOUT FURTHER INCIDENT. AN EMERGENCY WAS DECLARED. MAINTENANCE REMOVED AND REPLACED THE CAPTAIN'S L1 WINDSHIELD ALONG WITH THE L1 WINDOW HEAT CONTROLLER, AS PRECAUTIONARY. OPERATIONAL CHECK GOOD PER JOB CARD J356-11-01.