[sigmoid10]

If wings only generated lift in one direction (i.e. towards the curved side), then even flying with your nose up would pull you down if you are inverted. What people here are missing is that curved wings in level flight generate lift, but any shape of wing can generate lift with a positive angle of attack. Just stick your hand out the window while driving on the highway and tilt it slightly, you'll see.

[clairity]

> "Just stick your hand out the window while driving on the highway and tilt it slightly, you'll see."

this is really all the intuition most people need to understand flight, even if it leads to an incomplete understanding. it's easy to feel the air pushing on the bottom of your hand when you tilt it up (or top, when tilted down). what's not obvious is that there is also lift created on the top side at the same time, but that can subsequently be learned in high school physics (or fluid dynamics in college, which is where it really stuck for me).