Last week, as I returned to my rental FBO after an evening local flight, the
clerk on duty said an instructor and his student were stuck at an airport
about 40 minutes away. I spoke to the instructor on the phone and I agreed
to fly up and bring them back. He mentioned that, of course, I wouldn't
have to pay for the aircraft time. Did I violate the terms of my PPL by
accepting free time in the airplane as "compensation" for picking them up
and bringing them back? Should I therefore have paid a proportional share
of the costs?