wrote:
I'm sure I've come across posts from people here who seem to fly more
than one type of plane at a time, so I guess it's legal in the US to be
able to do so.

I don't think most of us have the skill to fly more than one airplane at
the same time. Bob Hoover maybe. I know he can pour a glass of water
from a pitcher while simultaneously performing a barrel roll. :-)

Matt