That's interesting, I wonder what happens if you take one of the current prototypes and hover off the ledge of a canyon... Will you drop suddenly and go splat, or will you keep altitude? Intuition says the former, but I'd like to know objectively.

If you're flying high enough before going over the cliff, you'd keep hovering... it's no different than a helicopter. These jets can definitely fly that high.

That said, if you're not flying high enough... if it's just the jet pushing air against the ground... you will go splat.