How is the autothrust system engaged in flight?

The autothrust system on the A320 is engaged in flight primarily by setting the thrust levers into the designated engagement range. This means that when the thrust levers are moved to a position within this range, the system detects this action and activates autothrust, allowing for automatic control of thrust during various flight phases.

This method allows the flight crew to utilize the autothrust system effectively by managing engine thrust through the thrust levers rather than relying solely on switches. It is designed to enhance performance and efficiency, ensuring that the thrust maintains optimal levels as required by flight conditions.

The other options do not accurately reflect the process for engaging the autothrust system while in flight. Understanding the mechanics of how the autothrust engages enhances awareness of operational protocols and contributes to safe and efficient aircraft handling.