Originally Posted by abelenky

This answer is coming from a student, so I'm hardly authoritative, but here's my best understanding.

For physics purposes, lift is variable, true.

But for many flight-purposes, lift is either greater than aircraft weight ("On"), or less than aircraft weight ("Off").

It doesn't matter if your wings are generating lift (in the physics sense), if the lift is less than the aircraft weight. You're still falling. So for flight-purposes, you have no usable lift.

If the lift generated exceeds aircraft weight, you're flying.