Which part of the aircraft must the first pilot check before the Exterior Inspection?

Before conducting an Exterior Inspection, the first pilot is required to check the ejection seat safety pins. This step is crucial for ensuring that the ejection seat is safely inoperable during the inspection process. Checking the safety pins prevents accidental ejections and enhances overall safety for the pilot and ground personnel during pre-flight checks.

While the other options relate to important aspects of aircraft operation and safety, they are typically not the immediate concerns that need to be checked before the exterior inspection begins. The AOA system, cockpit instruments, and fuel gauge readings are critical checks but are part of different stages of pre-flight preparations or inspections that involve the operation of the aircraft or its systems, rather than ensuring the immediate safety of personnel during an exterior inspection.