Mash bananas in a large mixing bowl, then add egg, brown sugar, olive oil and vanilla extract. Stir well to combine.
Sprinkle flour and cinnamon on top and fold together until just combined.
Divide the mixture evenly into muffin cases (silicone or paper) and carefully place into the air fryer basket.
Slide the basket into the air fryer and bake on 160C / 320F for 15 minutes or until muffins are golden and a skewer comes out clean. If you have a smaller air fryer you may need to do two batches.
Move to a wire rack and allow the muffins to cool in the cases.
