Final answer:
To engage the aircraft level attitude recovery mode when in an unusual attitude, the aircraft must be above a certain speed known as the maneuvering speed.
Step-by-step explanation:
In order to engage the aircraft level attitude recovery mode when in an unusual attitude, the aircraft must be above a certain speed. This speed is known as the maneuvering speed and it is usually indicated by a red line on the airspeed indicator. The exact speed may vary depending on the aircraft, but it is typically around 120-150 knots.