Dan, any flight is eventually paid for by someone.
What constitutes a fare paying flight (or commercial flight) is that the beneficial owner or someone representing him pays a compensation for the flight.
What constitutes a non fare paying flight is that the pilot or the operator of the flight bear the whole cost of the flight.
A cost sharing flight is somewhere in between.the two.
A flight whose cost is wholly paid by the operator can be flown under FAR 91 and have a PPL at the controls if the pilot is the operator or if there is no transportation of passengers or goods.
If these conditions are not fulfilled, the pilot must be a CPL.
This flight with a CPL pilot is then validly flown under FAR 91 with the condition that the pilot and the plane have not been brought together to the person paying and organising the flight.
If they have been brought together, the middle man must be considered as the real flight operator and proposing a commercial transport service under FAR 135.
So, it is not the fact that the flight was made for the sole purpose of transporting a passenger that necessarily makes it a commercial flight.
If you, as a pilot, make a flight just for transporting a friend at no charge, that's not a commercial flight.
Last edited by Luc Lion; 8th Mar 2019 at 17:21.