In a medium sized mixing bowl, combine the flour, garlic powder, ground black pepper. Preheat the air fryer to 350° F. Dip banana peppers into the seasoned flour, and let them sit for 5 minutes to get a thick flour coating. Place the coated banana peppers in the air fryer basket in a single layer. Spray cooking oil all over the banana peppers on both sides. Air fry the banana peppers for 8 minutes, or until golden brown. Move the banana peppers onto a baking sheet lined with paper towels to remove any extra oil, let them cool for 5 minutes before serving. For serving, move the dish onto a platter or a bowl and pair it with a small bowl of ranch dressing for dipping.