Originally Posted by
RJ85FO
I believe this is a common misconception. It is my understanding that Flight Instruction does not count as "Commercial flying" with regards to 121.471 as it is does not fit the definition of "air commerce."
Actually I think it is a misconception that it doesn't count toward your commercial flight time limits. We went through this not to long ago on here, I was able to find some FAA interps stating it goes against 121 and 135 flight time limits, however the search function on this forum stinks so I can't pull up the thread.
FWIW, ALPA produced a little booklet about flight time limits and it also said flight instruction counts against your limits. I'm too lazy to look it up now but someone might be able to produce it.