Ephesians 2:2 calls the spirit at work in the sons of disobedience the ruler of the power of what?

Answer: The air

They once walked according to the ruler (KJV: prince) of the power of the air, the spirit now at work in the sons of disobedience.

“in which you used to walk when you conformed to the ways of this world and of the ruler of the power of the air, the spirit who is now at work in the sons of disobedience.”— Ephesians 2:2 (BSB)