Who is allowed to occupy the back seat of any ATP aircraft without prior approval?

In ATP operations, the policy is that no one is allowed to occupy the back seat of any ATP aircraft without prior approval. This is primarily for safety and operational integrity reasons. Each individual on board an aircraft must be accounted for and must have a specific role in relation to the flight being conducted. Unapproved passengers could pose distractions or complicate emergency situations, hence no unauthorized personnel may occupy seats during flight without explicit permission and the requisite safety briefings.

In this context, even though current instructors, flight examiners, and ATP mechanics may have qualifications or reasons that could justify their presence in the back seat, the rules are strict in maintaining a controlled environment on board. Therefore, the only correct and universally applicable stance is that no one can occupy the back seat without prior approval.