Slice the bananas into thin rounds, about 1/8 inch thick.
In a bowl, toss the banana slices with lemon juice to prevent browning.
In a separate small bowl, mix together the sugar and cinnamon.
Drizzle the coconut oil over the banana slices or spray with cooking spray, then sprinkle the cinnamon sugar mixture evenly over them.
Preheat the air fryer to 350°F.
Arrange the banana slices in a single layer in the air fryer basket, making sure they are not overlapping.
Air fry the banana slices for 10-15 minutes, shaking the basket halfway through, until they are golden brown and crispy.
Remove the chips from the air fryer and let them cool completely before serving.