Which of the following is NOT an indication of an aircraft preparing for pushback?

The indication that the beacon is off is not associated with an aircraft preparing for pushback. Typically, when an aircraft is about to push back, the beacon light is activated to signal that the aircraft is preparing to move and to alert ground personnel and nearby vehicles of its status. This is a safety measure that helps prevent accidents during ground operations.

In contrast, engines running, cones being removed, and the tug or towbar being attached are all positive indications of preparing for pushback. When engines are running, it shows readiness for the aircraft to move. The removal of cones, which are safety markers, indicates that the area is clear for movement, and attaching a tug or towbar is essential for facilitating the aircraft's pushback from the gate. Each of these actions contributes to the pushback process, while the stillness of the beacon reflects that the aircraft is not yet ready to be pushed back.