karl gruber wrote:
...
The rulings don't have to make common sense. You must have commonality,"
which means you can't fly someone around for their convenience. That's 135.

IOW, if I log the time in my own plane, it's 135. If not logged,
it's permissible. FAA's legal opinions on 135 are on their web
site, and I don't think there's one which would stretch a favor
for a friend that far. They often decide a 135 issue based upon
the expectations of the passenger. So, if I fly a pilot/friend to
another field to retrieve his airplane, for no payment (cost
sharing prohibited if no common purpose), that pilot/friend is
under no delusion I'm an air taxi operator. And one who flies
charter for free. I make it up in volume. :-)

Fred F.