As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLIGHT 399 FROM KBWI TO KDAY AT FL 330 CO-PILOTS SLIDING WINDOW OUTER PANE EXPERIENCED MULTIPLE CRACKS EMANATING FROM FWD LWR CORNER. AIRCRAFT DESCENDED TO FL 010 AND DEPRESSURIZED CABIN. AIR TURNBACK TO KBWI WITH NO FURTHER INCIDENTS.