Final answer:
The primary force that allows an airplane to turn is the lift force, which is redirected horizontally when the airplane banks. This horizontal lift is what causes the airplane to accelerate in a new direction, explaining the sensation of being pushed due to inertia in a noninertial frame of reference.
Step-by-step explanation:
The primary force that causes an airplane to turn is the lift force generated by its wings. When an airplane turns, it achieves this by banking, which means tilting its wings relative to the horizontal plane. As the airplane banks, a component of the lift force that usually acts in a vertical direction to balance the weight of the airplane is now directed horizontally. This horizontal component of the lift force is what causes the plane to accelerate in the direction of the turn. Physicists refer to this concept when discussing inertial forces and noninertial (or accelerated) frames of reference such as what happens in tight turns, where a person feels like they are being pushed outward due to their inertia, but in reality, they are experiencing the effects of their own inertia and the change in direction of the vehicle or object they are in.