Aircraft A-300 AP-BAZ was on a schedule domestic flight PK-300 from Karachi to Islamabad. The departure from Karachi was on time. The weather enroute was fair and the flight was uneventful. Islamabad weather was cloudy with traces of cumulonimbus clouds with light drizzle. After clearance from Cherat, the aircraft started to descend. Light turbulence was felt during descent.