What was found
(CAN) APPROX 15 MINS AFTER LEVELLING OFF AT CRUISE ALTITUDE OF 29,000 FEET, SMALL CRACK FORMED ON RIGHT WINDSHIELD. FEW SECONDS LATER, ENTIRE INNER PLY SHATTERED & CABIN PRESSURIZATION LOST AT RATE OF APPROX 2500 FT/MIN . EMERGENCY OXYGEN DEPLOYED & MASKS DONNED, & EMERGENCY DESCENT TO SAFE ALTITUDE OF 11,000 FEET CARRIED OUT BY CREW. A/C CARRIED ON TO MEDICINE HAT (CYXH), WHERE UNEVENTFUL APPROACH & LANDING WERE CARRIED OUT. INSPECTION OF WINDSHIELD UPON ARRIVAL CONFIRMED THAT ENTIRE INNER PLY HAD SHATTERED. HAD BEEN NO PREVIOUS REPORTS OF DAMAGE ON WINDOW,&WINDHSIELD HEAT OP NORMAL.INSPOF FUSELAGE WINDSHIELD ATTACH STRUCTURE REVEALED NO ABNORMALITIES. REPLACED WINDSHIELD.