AES wrote:

So, how does a frisbee fly, anyway? Another of his favorites is just a
10" diameter weighted outer rim filled in with a slightly saggy "cloth
drumhead", which visibly bulges upward 1" or so at the center into a
fair imitation of an airfoil when you throw it. I've always figured the
heavy rim kept the thing spinning and thus semi-rigid, and the forward
motion of the airfoil shape gave the lift.

That, and a positive angle of attack. The spin keeps it gyroscopically
stable. As the forward motion decreases the Frisbee begins to settle,
increasing the angle of attack until becomes a kind of parachute. But
not always. Throwing the Frisbee up will give it a positive angle of
attack as it climbs. Once the forward motion stops the angle of attack
can become negative, generating downward lift and causing the Frisbee
to accelerate downward and back toward you like a boomerang. It comes
down faster than it would simply fall and it accelerates the whole way.