[cinFLA]

Forward thrust results partially from conservation of momentum: by throwing air molecules backward, the propellor experiences a motive force in the opposite direction, as a consequence of Newton's Third Law of Motion. To me, "pushing air backward" is an acceptable way to state this, when one trusts that the audience understands the physics of motion. Although the pressure gradient created by the action of the propellor also contributes to the thrust vector, failure to mention this component of the thrust is not a sin in this context.

Are you saying momentum is not conserved and that the "pressure gradient" contributes but not in a way that conserves momentum? I think I will have to take issue with that.

[sourcery]

Are you saying momentum is not conserved and that the "pressure gradient" contributes but not in a way that conserves momentum? I think I will have to take issue with that.

Oof. That's not what I meant, but I see why you might take it that way. The fault lies entirely with my wording.