Generally speaking, if you are consuming the instructor's time, you
should
be paying for his time. This includes supervised solos, when the
instructor is (should be) monitoring your flight and is focused entirely
on you.


I agree, and so does my instructor it seems. The first solo where he stood
on the flight line, I paid him for his time. When I've gone on my solo cross
countries, I don't pay him. However, I do pay him when (usually the day
before the flight) we review my flight planning and (usually just before the
next lesson) we discuss how the flight went. The day of a solo x-c we'll
talk on the phone or he'll meet me at the flying club and we'll make sure
we're on the same page as far as weather, TFR's, etc., but I don't pay him
for that time since it's just a few minutes. Similarly, if I'm just going up
solo for pattern work or air work over the harbor, I'll get the OK from him
on the phone or during the previous lesson and won't need to pay him since,
for all I know, he's 100 miles away doing his own thing while I'm in the
air.


-Tony
Student Pilot
40.4 hours