zlacker

Flat wings can and do fly just fine, they are just a bit less efficient. The teardrop shape and camber/cupping underneath just make the winds more efficient at slicing through the air without creating as much turbulence and drag.

>>AngryD+(OP)
My understanding is that "less efficient" here mean that flat wings have, specifically, less desirable stall behavior. Flat wings will stall more easily than an appropriate shaped "teardrop" wing.

A "stall" happens when the wing is no longer directing air downwards (and thus not providing lift), and is instead just chopping up in the air into turbulent chaos without any consistent direction.