I saw the verb ''fall'' with all 3 prepositions, I'm not sure, whethere all of them are correct or not.
Sometimes airplanes fall from the sky and strike houses.
Sometimes airplanes fall out of the sky and strike houses.
Sometimes aiplanes fall off the sky and strike houses.
Thank you for your response.
Something can only "fall off" something if it was already "on" it. An aeroplane is not "on the sky". It's "in the sky".