During which phase of flight does the aircraft begin to level off at cruising altitude?

The phase of flight where the aircraft begins to level off at cruising altitude is the cruise phase. During this phase, the aircraft has already taken off, climbed to its designated altitude, and established stable flight. Once the aircraft reaches the cruising altitude, it transitions from the climb to level flight, allowing for efficient fuel consumption and passenger comfort.

In contrast, the takeoff and climb phase involves the aircraft's ascent from the ground to reach cruising altitude, and the pushback and taxi out phase refers to the time spent maneuvering on the ground before taking off. The landing phase occurs as the aircraft descends and prepares to touch down, which is not related to leveling off at cruising altitude. Therefore, cruise is the correct phase when the aircraft maintains a steady altitude after climbing.