ORIGINAL: Tim Green
when something changes the momentum of the air, that something will react with a force equal to that momentum change and in the opposite direction.
Agreed (as long as by "momentum change" you mean "rate of momentum change"). My issue is you have been arguing the converse of this... that when something (e.g. air) exerts a force on another object it will experience a rate of change of its momentum. This is true ONLY if that something experiences an UNBALANCED force.
You illustrated a few posts back that a RC helicopter hovering over a scale results in the air experiencing no unbalanced force (upward force exerted by the scale on the air is equal and opposite the downward force exerted by the helicopter on the air). If you don't conclude from this that the air is experiencing no net rate of vertical momentum change, then you truly do not understand Newton's Second Law.
You have stated over and over again that a lifting wing imparts net vertical momentum to the air, yet you have provided nothing to show that a wing imparts more downward than upward momentum (other than a flawed argument that Newton's Laws require this to be the case).