Bake the loaf: Heat the oven to 350°F. Grease a 9-by-5-inch loaf pan.
In a large bowl, mix the mashed bananas, melted butter, brown sugar, eggs, bourbon, and vanilla.
Add the flour, baking soda, salt, and cinnamon. Stir just until combined; don’t overmix.
Pour the batter into the pan. Bake for 55–65 minutes, until a toothpick inserted in the center comes out clean. Cool completely before slicing.
Air-fry the slices: Cut the loaf into thick slices and lightly butter both sides. Place in a single layer in the air fryer basket.
Air-fry at 375°F for 4–6 minutes, flipping halfway, until golden and crisp. Cook in batches if needed.
Serve warm with maple syrup or vanilla ice cream.