Starting from level flight, the pilot pitches the aircraft up about 10 to 30 degrees above the horizon, into a brief climb. The purpose of pitch-up is twofold. This causes an increase in altitude which minimizes altitude loss and airspeed gain. As the aircraft begins to roll, it starts to lose lift. When the wings are vertical, the only lift generated is a small amount from the fuselage, and the aircraft will begin to lose altitude. The brief climb compensates for the loss, allowing the aircraft to complete the roll at the same altitude the maneuver began. When the aircraft is completely inverted, the increased pitch results in greater angle of attack, enabling the inverted wing to generate lift.