In an aircraft, which position is directly responsible for acting as a co-pilot?

The position that is directly responsible for acting as a co-pilot in an aircraft is known as the First Officer. The First Officer assists the Captain in operating the aircraft and is trained to take control in case the Captain is unable to perform their duties. This role is crucial for ensuring safety and efficiency during a flight, as the First Officer shares the workload involved in piloting, such as navigating, communicating with air traffic control, and managing flight systems.

The Captain, while also a pilot, holds the primary responsibility for the aircraft and the safety of those on board; therefore, they are not in a co-pilot role. The Flight Attendant is focused on passenger safety and comfort, handling in-flight services and emergencies, but does not operate the aircraft. The Operations Manager is involved in broader operational aspects of the airline but does not have a direct role in the cockpit during flights. Thus, the First Officer is specifically designated as the co-pilot, making this the correct answer.