Originally Posted by EMAW

Almost. Part 135 passenger ops always requires an SIC (135.101), no matter the seats, UNLESS the operator has OPSPEC A015 which allows an autopilot in lieu of SIC AND the aircraft has 9 passenger seats or less. (135.105)
If the aircraft has more than 9 passenger seats, you can’t use A015 and therefore an SIC is always required. 135.99 (b)
My company doesn’t have A015 therefore, under 135, an SIC is required even though we only have 9 passenger seats.
In other words, the regulations require an SIC. The OPSPECS give you relief under A015.