Which flight function is seldom utilized except during takeoff and landing or in emergencies?

Manual flight is the correct option because it refers to the operation of the UAS by a pilot directly controlling the aircraft using physical controls. This approach is typically required during critical phases of flight such as takeoff and landing because it allows the pilot to react more quickly to changing conditions and exercise greater control. Additionally, manual flight is essential during emergencies when immediate, hands-on decision-making is crucial to ensure the safety of the UAS and those on the ground.

Although other types of flight, such as autonomous flight and remote flight, can cover most of the mission's operational aspects, manual flight remains vital for those specific times when safety and situational awareness are of utmost importance. This minimizes reliance on automated systems that may not adapt as effectively in unpredictable circumstances.