Originally Posted by
Gvdriver
Actually under 91 there is a reg that prohibits a crew member from leaving his station unless nature calls.There is nothing that states that a non pilot cant sit in the pilot seat but we are talking about a high performance jet @ fl410 and the pax is a non pilot who needs more than flight instruction to sit there ..
Physiological break could include stretching, and like you said nothing says the pax cannot sit there when the pilot is taking his break. Not suggesting it's a great idea.
But if the OP did not need a break, that would be grounds on his part to refuse to vacate the seat.