For companies that operate P135 single pilot type rated aircraft such as King Air 300/350, Premier & Citation aircraft as long as they are approved for single pilot 135 there is no requirement for an SIC. That being said often times the insurance companies and/or the charter brokers have requirements for a "second pilot" to be on board these aircraft for insurance reasons. They often refer to these pilots as "safety pilots" These pilots are not required by the FAA to be trained in any way on your aircraft however they are counted as a passenger on the manifest (they are not supposed to conduct any duties as a crew member in any way). Often times I have seen or heard of companies using this seat as a way to train and cultivate inexperienced pilots. This is definatly in the "gray area" as these "seat fillers" are not supposed to be doing anything but observing. These "passengers" could be in uniform as they are just a company rep at that point. I do not see any legal issues with it, maybe a liitle bit of misleading the customers.

How does 9K work around this as they are an FAR Part 135 single pilot operation, but have F/O's logging SIC time in the right seat of the C-402?

I've seen this question come up alot in this forum. I believe it's been answered in the Cape Air thread.

Might also check you GOM... Ours, for instance, has a prohibition against anyone but a company trained pilot from occupying any pilot seat in the aircraft...