NBAA's interpretation for this set up is that all flights have to be 135. I don't buy it, but it begs the question who is responsible for determining 91 vs 135. The question came up because our boss wanted us to fly a friend of his who he has business dealings with, but no official connection to our company and they said it would be a 91 flight - i.e. no money changing hands. To what extent do I have to determine the financial transactions that take place? Our flight department is in a LLC whose sole purpose is to provide air transportation and we have our own 135 certificate. The aircraft is registered in the LLC which the owner is president of and the parent holding company. The family of the company uses the plane and I believe they use the Standard Industry Fare L.... (SIFL) set up to account for tax liability for the use of the airplane. I don't no how they handle the expenses from a trip. NBAA said it would be different if the company that operated the airplane had its main business in something other than providing air transportation and then the family use of the airplane could then be called incidental to the business. Is there a legal opinion out there that says if the use of the company plane is by company employees or family it's 91? Our intention is to document the owner's friend's trip as 135 whether or not the get any "compensation" from it.