Yeah, I think you guys are talking about different scenarios. A repositioning flight, a charter, and a maintenance ferry all have different rules. By the regs, a maintenance ferry where the aircraft is flown in a non-standard configuration, engine out ferry on a 4 engine a/c for example, is limited to required flightcrew members. Line UAL pilots no longer see these segments as we have engineering & test pilots to fly them.

Repositioning flights can carry F/A's, and I've carried offline jumpseaters on those segments.

Charters are owned by the charter department and can make up their own rules within FAA regs.

Dedicated cargo flights, RIP, also had the ability to dictate who flew on the aircraft sans F/As