It largely depends on JS agreements across carriers. I have no clue of the relationship between Atlas and Net Jets. It would surprise me that one exists given it would be pretty tough for a 121 pilot to catch a ride on Net Jets. Would the NJ airplane have to be empty? A lot of those planes don’t have Jumpseats. If I were a paying member of a fractional I would be annoyed if a random person was on my flight. Please correct me if I’m wrong.