All over it. Gravity attracts every molecule in the Universe to every other molecule. When you leave your seat and walk to the rest room while in a plane, it is gravity that holds you down to the floor. As a simplifying approximation, engineers often treat gravity as applying a force on the center of mass of an object.
It would float away into space and implode.
If you were on a plane and had no weight to you you would float in the plane like there was no gravity, even though there is but if the plane was angled precisely you can float in the plane as if gravity was turned off. But this only lasts a few minutes as you come closer to land.
Gravity on a plane is less then on a hill because you are away from the earth, However gravity in a plane over a hill is more then gravity on a plane over a valley at the same altitude above sea level.
If a plane is in level flight, gravity (weight) is equal to lift.
If you were going to treat all of the forces acting on a plane at a specific point that point would be the CG (Center of Gravity), which is usually measured in inches aft of the datum (a non-physical point used by engineers to define the center of gravity).
lift.... Gravity
Yes, you can experience free fall in a plane, but normally this would only happen for a short period of time. There is only so long you can do this before pulling up or hitting the ground.
an example of gravity is sky diving. the gravity is pulling down the the ground after you jump out of the plane.
Gravity
gravity
Because of the gravity
Gravity and the skill of the pilot.