91 vs. 135 have EVERYTHING to do with the subject.
The FAA does not define a “commercial operation” well. The National Business Aircraft Assn. petitioned the FAA years ago to allow limited compensation years ago–the FAA wouldn’t change the law, but WOULD grant an “exemption” from the ill-defined law every year–BUT ONLY TO NBAA MEMBERS.
Some examples–Several owners of corporate aircraft want to utilize the aircraft of another aircraft based on the field. The only way they can do this is to all join NBAA and partake of the exemption. They can trade hour for hour on each other’s aircraft, (“Interchange”) but what if there are two or more different types of aircraft? They can work out an hourly trade ratio–“3 hours on my aircraft for 2 on yours” for example–and if they don’t use the trade time–they can compensate for cash. A clunky “work-around”–nobody is safer because of it.
Some companies go to the extreme of “'selling” a portion of their aircraft to another to avoid the onerous “charter” regulations–this can be as little as 1/16 of the aircraft (“fractional ownership”)
In the case of turbojet aircraft (but not prop planes) the FAA wont allow charging, but allows “double the fuel costs” since the jets burn so much more fuel.
What if an aircraft owner wants to allow a friend to use his airplane? CAUTION: POSSIBLE CHARTER!
What if that same owner is going to a destination, and a friend wants to go along? MAYBE a split on the fuel is legal–but not a charge on the airplane. What if the friend wants to be dropped off at a spot enroute? (???)
I’ve managed and crewed multiple airplanes for years–and always make it a point to ask the owner the purpose of the trip and the involvement of the passengers–for my protection as well as the owner. The owners resent it–but we’ve never had an FAA violation–I refuse the trip without these answers.
It goes back to the safety factor, again. "How is it that the (relatively) unregulated Part 91 operators–flying the very same airplanes–have a BETTER safety record than the highly regulated Part 135 Charter operators? How is it that the U.S. Part 91 operators have a BETTER safety record than the highly regulated operators in the rest of the world? How is it that PART 91 insurance is so much cheaper than Part 135? How is it that the preponderance of Part 91 operators choose NOT to put their very expensive airplanes to work under Part 135, and pay the higher cost per flight hour NOT to put their airplanes to work? Why is it that the majority of pilots would RATHER fly corporate than charter?
The FAA is killing the industry with over-regulation in the name of “safety.” As one British wag summed it up–The CAA in Britain considers it a failure every time an aerocraft takes off, as there MIGHT be a crash!"