As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WHILE IN CRUISE AT FL340 R1 WINDOW BEGAN ARCING IN LOWER LEFT CORNER. HEAT WAS REMOVED AND A SUBSEQUENT CRACK FORMED FROM THE ARC SPOT UPWARD AND INWARD TOWARDS THE CENTER FRAM. THE CRACK APPEARS TO BE LIMITED TO THE OUTER PANE. GROUNDED - YES. REMOVED AND REPLACED R1 WINDOW REF B737-900 AMM 56-11-11-400-801. OPS CHECK LEAK CHECK GOOD.