From Stick and Rudder by Wolfgang Langewiesche, page 9, published 1944:

The main fact of all heavier-than-air flight is this: the wing keeps the airplane up by pushing the air down.

It shoves the air down with its bottom surface, and it pulls the air down with its top surface; the latter action is the more important. But the really important thing to understand is that the wing, in whatever fashion, makes the air go down. In exerting a downward force upon the air, the wing receives an upward counterforce--by the same principle, known as Newton's law of action and reaction, which makes a gun recoil as it shoves the bullet out forward; and which makes the nozzle of a fire hose press backward heavily against the fireman as it shoots out a stream of water forward. Air is heavy; sea-level air weights about 2 pounds per cubic yard; thus, as your wings give a downward push to a cubic yard after cubic yard of that heavy stuff, they get upward reactions that are equally hefty.

That's what keeps an airplane up. Newton's law says that, if the wing pushes the air down, the air must push the wing up. It also puts the same thing the other way 'round: if the wing is to hold the airplane up in the fluid, ever-yielding air, it can do so only by pushing the air down. All the fancy physics of Bernoulli's Theorem, all the highbrow math of the circulation theory, all the diagrams showing the airflow on a wing--all that is only an elaboration and more detailed description of just how Newton's law fulfills itself--for instance, the rather interesting but (for the pilot) really quite useless observation that the wing does most of its downwashing work by suction, with its top surface. ...

Thus, if you will forget some of this excessive erudition, a wing becomes much easier to understand; it is in the last analysis nothing but an air deflector. It is an inclined plane, cleverly curved, to be sure, and elaborately streamlined, but still essentially an inclined plane. That's, after all, why that whole fascinating contraption of ours is called an air-plane.

Don't miss their updated PDF version: http://www.allstar.fiu.edu/aero/Flightrevisited.pdf

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Important but somewhat complicated point: flight in a 2D world is a venturi effect, and regardless of altitude, a two-dimensional airfoil remains trapped in "ground effect mode." The circulation extends outwards indefinitely, and so an instant force-pair connects the wing with the surface of the Earth.

In 2D, the airfoil circulation creates lift upon the moving airfoil, but it also creates an equal down-force against the ground. If the airfoil was flying higher, the force pattern on the ground grows wider, but the net downforce doesn't change. As a result, 2D airfoil diagrams do not describe normal flight. They describe a sort of "Flatland flight" where no net work needs be done to accelerate mass downwards. As an explanation of aircraft, they've been simplified until they cross the line into actual error.

In the 3D world we can launch a vortex downward and experience a reaction force upward. Or perhaps launch a vortex sideways (during turns.) No instant-force upon the Earth is needed. The Newtonian force-pair arises between the mass-bearing aircraft and the mass-bearing air entrained by the shed vortex. Hovering rockets have an exhaust plume, and flying airplanes have a descending vortex-pair, and both are essential to any explanation. Real world 3D flight is "vortex-shedding flight," and the explanations based on 2D airfoil diagrams leads to no end of confusion.

See also, the awesome Amasci site discussion of this:

http://amasci.com/wing/airfoil.html

http://amasci.com/wing/rotbal.html

http://amasci.com/wing/whyhard.html

edit: Another interesting fact is that the flawed description of how airplanes fly is so pervasive that Albert Einstein once proposed how to improve the airfoil based on his understanding of it and it was a huge flop.

See the end of this article:

http://www.mathpages.com/home/kmath258/kmath258.htm

http://xkcd.com/803/

(obligatory mention)

A lot of this stuff also applies to sailing, a great website that I've been preaching for years that focuses on the Coanda Effect is http://sailtheory.com I highly recommend

This is great.

I usually tell people that planes fly by pushing air down and backward: down so the airplane doesn't fall and backward so the airplane moves forward. I tell them this because otherwise they completely forget, and jump into assertions about implementation details like laminar airflow.

Now I know to _first_ talk about air going backward and down and _then_ to point them at the conclusions section of this article, referring them to the body of the article for detail. A-and then I'll get back to my work so I can get home at a decent hour.

This is a largely correct article debunking one of the main atrocities in aerodynamics education today. I approve heartily!

NASA's explanation of how the "Longer Path", or "Equal Transit Time" theory is incorrect.

http://www.grc.nasa.gov/WWW/K-12/airplane/wrong1.html

The page contains a simulator of a symmetrical airfoil that you can tweek, angle of attack, particle flow, velocity, and pressure - as well as instructions for experiments proving this theory incorrect.

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A couple of recent blog posts linked to the fiu.edu article. They may also be interesting reading:

Kevin Drum: The Problem With Science: http://motherjones.com/kevin-drum/2011/12/problem-science

Modeled Behavior: Of Science and Scientism: http://modeledbehavior.com/2011/12/21/of-science-and-scienti...

Can we not easily test the equal-transit-time explanation by a smoke test in wind tunnel where the the smoke is not released continuously but only at uniform time-intervals in a vertical profile? A picture of the smoke profile (as opposed to streamlines) downstream of the wing would immediately capture the fact that transit times are NOT equal.

FIU on HN? Ha, go golden panthers!