Peel the bananas and slice them into thin rounds, about 1/8 inch thick.
In a small bowl, mix the granulated sugar and ground cinnamon together.
Place the banana slices in a large bowl and drizzle with lemon juice. Toss gently to coat the slices evenly.
Sprinkle the cinnamon sugar mixture over the banana slices and toss again until well coated.
Preheat the air fryer to 350°F (175°C) for about 3-5 minutes.
Lightly spray the air fryer basket with cooking spray or brush with a small amount of oil to prevent sticking.
Arrange the banana slices in a single layer in the air fryer basket, making sure they do not overlap.
Air fry the banana slices for 10-12 minutes, shaking the basket halfway through to ensure even cooking, until they are golden and crispy.
Remove the banana chips from the air fryer and let them cool completely on a wire rack. They will become crispier as they cool.