The issue is not that they operate under Part 91, but what equipment and training they use. If they meet the equipment and training of Part 135, even if they are operating under 91, that's OK. If they use 91 to skimp on equipment, that's poor headwork.
Some oil companies use unstabilized 212's offshore at night. That means that oil workers are exposed to extra safety problems because their companies use Part 91 to hide from reasonable safety rules. Does their senior management know that the simple requirements of Part 135 are not followed by their professional transport sections?
If you are offshore at night, you are in instrument conditions, and you should be in a helicopter equipped to handle instrument flight. What a meaty ground for law suits from the families of passengers lost in accidents. It is amazing that in the 21st century, this common sense safety concept is ignored!
Those oil passengers should be told what their company is exposing them to, and that the cheapest fleabag Charter operator in the US has higher safety standards! Pass the life jacket, please, and sit me next to an exit.
