Newtonian versus Bernoullian lift explanations is a tough topic, quite obviously. Equal transit time theories can be thrown away immediately - windtunnel tests with smoke-injected airflow indicates that the air above the wing certainly doesn't always reach the wing trailing edge at the same time as its 'partner' - as well as some other silly and unfounded explanations. Of course, there's still Newton and Bernoulli to duke it out.
I think one of the key factors in deciding what actually creates lift is to make sure the definitions and concepts involved are concrete. For one, Bernoulli's equation (and Euler's) is really just a restatement of Newton's principle of conservation of energy/momentum/etc.; many things are not as mutually-exclusive as they seem. Pressure differences don't always indicate the 'presence' of Bernoulli, as Fred said - air striking the bottom of the wing and being turned (Newton) certainly exerts a higher pressure on that surface. Thus, the pressure-integration sort of method for calculating lift should hold true.
So which is it then, Bernoulli or Newton? Personally, I read too much conflicting info all from respectable sources to decide. Besides, it's more fun to sit back and watch.
However I must admit that, for the most part, I agree with John Anderson's explanation (below), but I feel that the boundaries between terms and equations and priciples are too thin and malleable to be just one thing or just the other.
John Anderson, author of many textbooks on aerodynamics (one of which I'm the proud owner of
), discusses this issue at length, and I think I agree with him for the most part. He first examines how air is accelerated when passing over a wing. Simply due to the shape of wings, air passing over the top 'senses' an obstruction and its cross-sectional area reduces accordingly (windtunnel smoke tests confirm this). Through mass continuity, we can see that because of that reduction in area, it's velocity increases. That's how the acceleration occurs. Anderson then claims that it is due to the Bernoulli effect that the increase in velocity on the upper surface of the wing lowers the pressure there (and, of course, creating a lifting force). As I said, though, Bernoulli's equation is really just a restatement of Newtonian principle, so any boundaries between the two are thin.
Anderson does go on to detail the "air-turning" (Newton) explanation of lift, but he says that it's not so much the fundamental reason why
lift is produced but it's more a result
of lift. Higher pressure on the lower surface of the wing still produces an action-reaction sort of situation, and the turning-down of the departing airstream still exists as well (higher-pressure air pushes the wing up and the wing in turn pushes the departing airstream down, completing the action-reaction pair). I think that just reinforces how blurred the differences between the two theories are.
There's also circulation which, again, is not so much a theory of how lift is produced, but another mathematical means for calculating it.
Well, I've rambled on long enough - and off-topic, as well! Sorry! I suppose sometimes it's just better to accept that "it flies," and get on with things. Quite interesting stuff, though...