From December 25, China Southern will completely replace Boeing 757 with Boeing 737-800 for flights between Urumqi and Islamabad. The airline's last Boeing 757 flight on this route is expected on December 23.
https://www.routesonline.com/news/38/ai ... -dec-2017/
In recent days mix of Boeing 757 and Boeing 737-800 has been used by the airline for Islamabad flights.
https://www.flightradar24.com/data/flights/cz6007
Abbas
