In a large bowl combine the flour, sugar, baking powder, baking soda, cinnamon, and salt. Set aside.
Mix the mashed banana, melted butter, and egg in a second bowl. Stir the banana mixture into the dry ingredients, mixing until just combined. Be careful not to over mix.
Place silicone muffin cups in the air fryer basket. You may need to do more than one batch depending on the size of your air fryer.
Scoop the batter into the muffin cups until ⅔ full and cook for 12-15 minutes or until a toothpick comes out clean.
Notes
These muffins will keep at room temperature in an airtight container for 5 days. They can also be frozen and will keep in the freezer for 3 months.