Thanks, I understand that there is an accelaration of air over the upper surface of a plane. Bernoulli's theorem applies to constant mass flow and is normally illustrated in a venturi which is a closed system. A free wing is not a closed system and need not necessarily have the same constant mass flow above and below the wing.
Bernoulli's theorem also applies along any streamline, and everywhere in irrotational flow (which this sort of flow is, within the fluid). A closed system is
not required.
If so how why don't I feel this under an aircraft, I would have expected a 230 tonne downforce shortly after rotation of a large jet would be quite noticeable in the area just off the runway?
The force on the ground
is there. It's spread over a considerable surface area though.