[lutorm]

Another good discussion about this is in the online pilot textbook "See How It Flies" at http://www.av8n.com/how/ (section 3). That author also disagrees with the Coanda effect conclusion.

The discussion in there is the best I've seen, it centers on the concept or circulation, the vorticity of the flow field around the wing. One example that's used is the fact that if you just take a wing by itself (try it with a long, flat piece of cardboard) it will "fly" while rotating in the air. It doesn't fly very well, admittedly, but it certainly exhibits a glide ratio a lot better than something with the same cross-sectional area that's not a wing. In that case, there's no top or bottom of the wing at all.

[arakyd]

Actually the whole av8n.com site is a great resource for anyone interested in learning more about physics. One of the reasons why I linked it ;).