The FAA does not consider part 91.501 flights to be commercial aviation, but the IRS disagrees. Excise tax applies to any amount that had to be paid to receive the air transportation. When payment is just in the form of cash, such as with the time sharing arrangement, the taxable amount is simply the amount paid. Hour trading interchange agreements are more complicated because the market value of the barter traded flight hours is taxable in addition to any cash true up paid. Although excise tax applies by default, it is possible that your operations may avoid the tax through an exemption. For example, if the transaction is between members of a qualifying corporate affiliated group or if the aircraft involved is less than 6,000 pounds gross takeoff weight. For example, when using the NBAA small aircraft exemption, which I discuss in another video.