How then, does it 'save time' if the student does the pre-flight before the
instructor arrives, if the instructor is going to do it again anyway?

The student's preflight is probably much slower. The instructor's
preflight probably concentrates on a few critical issues. The
instructor probably just flew that airplane a few hours ago. Not so the
student.

Jose
--
Humans are pack animals. Above all things, they have a deep need to
follow something, be it a leader, a creed, or a mob. Whosoever fully
understands this holds the world in his hands.
for Email, make the obvious change in the address.