Peel the bananas and slice them into thin rounds, about 1/8 inch thick.
In a mixing bowl, toss the banana slices with the avocado oil or olive oil until they are evenly coated.
Sprinkle the ground cinnamon over the banana slices and toss again to ensure even coverage.
Preheat your air fryer to 350°F (175°C).
Arrange the banana slices in a single layer in the air fryer basket. Avoid overcrowding to ensure even cooking.
Air fry the banana slices for 10-12 minutes, shaking the basket halfway through to promote even crisping. Keep an eye on them to prevent burning.
Once they are golden and crispy, remove the banana chips from the air fryer and let them cool completely on a wire rack. They will continue to crisp up as they cool.