How does an airplane fly upside down?

It works the same way. Most aircraft that fly upside down have a symmetrical airfoil, and it works either way. Of course, the wing is mounted on the fuselage for upright flying, so they angle of attack looks very different when an aircraft flies upside down. Lift is provided by the airflow over the wing, but also under. Think of an airplane, planing on the air, similar to how water skies plane on the water.

G'day, I found this: http://www.physlink.com/Education/askExperts/ae627.cfm I also found "A plane flies upside down. The physical view has no problem with this. The plane adjusts the angle of attack of the inverted wing to give the desired lift. The popular explanation implies that inverted flight is impossible." at http://www.allstar.fiu.edu/aero/airflylvl3.htm at the bottom of the article. I hope, this helps. The Wombat