Which door must be closed prior to closing the aircraft canopy?

The correct choice is based on the operational procedures pertinent to the F-35 aircraft, specifically regarding the safe and proper sequence for operating the canopy. Door 7104, typically known as the "loading door," must be securely closed before the canopy is closed. This is a critical part of the aircraft’s safety protocols, ensuring that the interior environment is properly sealed and preventing any potential hazards that could arise if the loading door remains open during canopy closure.

Operating the aircraft in accordance with these procedures is vital for both safety and maintaining the structural integrity of the aircraft during various flight operations. Each door on the F-35 has specific functionalities, and adhering to protocols is essential for efficient aircraft operation.