If the PIC is single pilot authorized then you can log the Part 91 "empty legs " in your logbook......iftwo pilots are required by the ops specs under Part 135 then you can log that as SIC if you are a 135 SIC if you have the checkride...i believe that is the case , correct me if i am wrong...CBIRE,hope you had a good Xmas, havent seen u on the forums lately Brotha!