In straight, level flight, the lift acting on the aircraft acts vertically upwards to counteract the weight of the aircraft which acts downwards. If the aircraft is to continue in level flight (i.e. at constant altitude), the vertical component must continue to equal the weight of the aircraft and so the pilot must pull back on the stick to apply the elevators to pitch the nose up, and therefore increase the angle of attack, generating an increase in the lift of the wing. The total (now angled) lift is greater than the weight of the aircraft, The excess lift is the horizontal component of the total lift, which is the net force causing the aircraft to accelerate inward and execute the turn.