As an engineer I can explain in very technical terms exactly what makes an airplane fly, however, it isn't easily understood by non-technical people. How can I explain it to a non-technical person, or a nine year old, in a way that isn't really incorrect but is far less technical than what we learn as pilots?
The simplest explanation is the "hand out of the window" one:
Hold your hand out of the window while in a moving car and hold your hand at an angle. It gets pushed upwards. Your hand represents the wing of an airplane. The plane's engine simply makes sure the "hand" keeps moving forward against the force of the wind.
Even a 4-year old understands the concept using this explanation.
Here's one way to do it: airplanes work by pushing air. The wings push air down, and the airplane turns by pushing air in different ways. Engines push air to the back, pulling the plane forward. Wings work by turning the air downwards--the airflow on the top of the wing follows the curve of the wing, which points it downward.
My apologies if this is too low-level--is this what you had in mind?
Every pilot knows the first thing that makes an airplane fly is money.
as I tried to explain the 4 forces to my 6 year old daughter and trying to coach her I asked, what makes it fall out of the sky. I expected weight or gravity and she said lack of money. She was right.
I try to explain it like a straw. You have four straws, one in front, one in back, one above and one below. The one below the aircraft sucks at a constant rate and never stops (gravity/weight). The one in front is the prop generating thrust. It is essentially sucking its way forward. The one in back is drag and it varies by situation but it's always trying to keep you from going forward. The final one is the one on top and that is lift. Lift is generated by the wings and sucks the airplane up. The wing creates lift by moving forward. If any of the straws win other than the front one and the top one, you crash.
As for wind, no you can fly through no wind but the addition of wind coming at you effectively helps fill that forward straw so you can essentially take off at a lower ground speed. This is called relative wind. If your plane flies at 54 knots and you could essentially fly into a 34 knot headwind at 20 knots and achieve backwards flight at 14 knots.
Blow over a sheet of paper that is lying on the table, and watch it take off. Then explain of course that there is a lot more air involved in keeping a 747 in the air, but you could make it plausible by mentioning how strong tornadoes and hurricanes are.