IMO, a Hobie Cat is on plane....(hell,
sometimes airborne)..when it is making better than hull speed.

Hobies have DEEP Vee hulls, not possible to plane.


Normally laden, all but a few inches of that
"Deep Vee" is above the waterline.

What's the effective draft of a Hobie Cat, in inches?

One could make a case that the boat is always, (effectively) on plane at least
as easily as a case that it cannot plane at all.

http://www.hobiecat.com/sailing/index.html

The exceptions prove the rule, as always.