Which term refers to the captain of the aircraft?

The term that refers to the captain of the aircraft is commonly abbreviated as "CA" or "Cpt," representing "Captain." The captain is the pilot in command of the aircraft, responsible for the safety of the flight, making key operational decisions, and ensuring compliance with all regulations. This role encompasses a broader set of responsibilities, including managing the flight crew and communicating with air traffic control.

In contrast, the other options refer to different roles within the cockpit team. The First Officer and Co-Pilot denote the same position, which is typically the second pilot who assists the captain and is qualified to fly the aircraft but does not have the final authority over it. The role of the Flight Engineer has largely been phased out in modern commercial aviation due to advancements in technology and automation, but it historically involved monitoring and operating the aircraft's systems. Thus, "CA" or "Cpt" is unequivocally the correct term for the captain of the aircraft.