What is the maximum number of passenger seats for smaller aeroplanes under part 135?

The correct option is based on the regulations outlined in Part 135 of the Federal Aviation Regulations, which govern commuter and on-demand operations. Under these regulations, smaller aircraft that fall into the category of "commuter aircraft" are limited in their passenger seating capacity to a maximum of 9 seats or fewer, not including the pilot seat.

This threshold is significant as it differentiates the operational requirements and regulatory oversight between different categories of air carriers. Aircraft with 10 or more passenger seats generally fall under Part 121 regulations, which impose stricter operational standards. Therefore, the limit of no more than 9 seats allows for more flexible operational aspects under Part 135 while ensuring safety and regulatory compliance for smaller aviation operations.