When is the need for a child restraint device in an aircraft applicable?

The need for a child restraint device in an aircraft is applicable when the infant does not sit with a parent. Regulations typically require that children under a certain age, often two years old, must be secured in an appropriate child safety seat if they are not occupying a seat with a parent or guardian. This is to ensure the safety of the child, as adult seat belts are not designed to effectively protect young children.

The rationale behind this requirement is based on the fact that infants and small children are especially vulnerable during flight due to the forces exerted during turbulence or in the event of a sudden deceleration. A properly secured child restraint device can provide the necessary support and secure positioning to minimize injury.

Other choices do not capture the essence of the situation effectively. For example, it is not solely dependent on the infant's age or the specific location of their seat. Additionally, factors like peak flight hours do not determine the need for a child restraint device; the priority remains the safety and secure seating of the child irrespective of the flight's timing or seating arrangements.