If you set the thrust to idle, the Bus will maintain flightpath until...
This is the theory. In practice it will roughly maintain the attitude, so you will need to increase pitch to maintain level flight.
The theory completely falls down when you start taking flaps when left to itself it will fail to maintain attitude or level, and the AP is not much better in the short term. So some skill / satisfaction can be had in flying to a better standard than the AP
NoD