1Preheat the air fryer to 155°C (310°F).
2In a small bowl, mix flour, baking soda, salt, and cinnamon (if using). In a larger bowl, combine mashed bananas, egg, sour cream, oil, sugar, and vanilla extract (if using).
3Gradually fold the dry ingredients into the wet mixture, stirring with a spoon just until combined. Leave a few small banana chunks for texture.
4Lightly grease a 18 cm (7-inch) loaf pan that fits in the air fryer basket with nonstick spray.
5Pour the batter into the prepared pan and carefully place it in the air fryer basket.
6Bake at 155°C (310°F) for 28 minutes, until a toothpick inserted in the center comes out clean with a few moist crumbs and the top is golden.
7Remove the pan from the air fryer and let it rest on a wire rack for 5 minutes.
8Place an inverted plate over the pan, then carefully flip to release the banana bread. Slice and serve warm, optionally with a drizzle of melted vanilla glaze.