Player direction in air

How can I make the player car to not be able to turn and change direction in the air?

You can shoot a ray from the car down and test collision. If the collision happens and the object (the road or whatever) has a distance greater than the root of the car and the bottom of the car, then you know it’s above ground and then you set a bool that is used to not allow turning… basically disable input until the ray that is being cast every frame gives you a road right under the car.