Which of the following is a function performed by a Federal Air Marshal?

The primary function of a Federal Air Marshal is to provide security and protection on flights. This role is crucial in maintaining the safety of passengers and crew, as well as ensuring that any potential threats are managed effectively. Federal Air Marshals are highly trained professionals who are responsible for identifying and addressing security risks, often working undercover to maintain a secure environment throughout the flight. Their presence is a deterrent against potential acts of terrorism and other in-flight disturbances.

The other options describe functions that do not align with the specific duties and responsibilities of a Federal Air Marshal. Monitoring air traffic control is primarily the role of air traffic controllers, while assisting in flight attendant training is typically a responsibility of management or training personnel within the airline. Managing passenger boarding processes involves airline staff and ground crews rather than federal law enforcement. Thus, providing security and protection remains the key and defining task associated with a Federal Air Marshal's role.