What is your suggestion?
In real life, when a plane is at a gate with a jetway, almost always the jetway is connected to the plane. This includes while the plane is not being serviced.
How would it work in the game?
In the game, this could be part of the arrival sequence (chocks, cones, etc.). Whenever a plane is at a gate with a jetway, they should be extended.
Why is this a good idea?
This would increase realism, especially at airports where there are not enough crew to handle every plane at the same time.