Interesting storyline, but lots of plotholes and inaccuracies.
1) The Actors are not fluent in Chinese
2) Their names are weird
3) The outside looks like a Boeing 777, but the Cabin looks like an A330/A340.
4) There is no way of accessing the cargo hold from the cockpit (although you can access the avionics bay)
5) I find it hilarious that literally at least 3 people died and none of the passengers seemed to notice. They are literally like NPCs. I felt that they could have been given more things to do, and they could have helped or deepened the plot.
6) There's absolutely no way the pilot would refuse to turn back after all that. If there's a criminal onboard, the Number 1 priority is to get the plane on the ground. There's no "Beijing's Orders" because the flight is supposed to be under ICAO laws and regulations. Even if they turn back, there's simply no reason the plane would have taken so much fuel that they are able to fly for so long, and decide to return directly back to Heathrow.