.........and the Typhoon is achieving what? Genuine question.
I would assume that the fighter pilot can visually check that the cabin is secure and the crew are indeed in charge of the flight.
I would also assume that if the aircraft varied from instructions given to it and for instance decided to crash dive into some area or other such as a nuclear power station then it might be shot down.
What I'm not clear on is how well the fighter plane would withstand a major explosion on the plane though I guess the amount of explosive carried by an individual would have limited spread.
I would like to see an answer as to why passengers on a plane with a suspected explosive device are not immediately evacuated.