I don’t think these vector diagrams are correct when they have the weight always pointing straight down. That situation is only possible when the weight is stationary.
if the aircraft is moving the weight is acting against that movement, along with the aerodynamic drag. (Modified by gravity of course)
so the W vector should be angled rearward by the addition of an inertia vector.
Taking all these vectors as they are usually displayed, as if the aircraft were stationary, Then remove the lift, thrust and drag, but leave the fact that the aircraft is moving, such as would happen if it left the atmosphere, then the aircraft would not just fall vertically down the W vector, it would continue forward/downward on a curved path as the inertia vector decayed to zero and replaced by W.