In a large bowl, whisk together flour, salt, and baking soda.
Place bananas in a medium bowl and mash until very smooth with a fork or potato masher.
Whisk in sugar, oil, sour cream, vanilla, and egg, making sure all ingredients are completely smooth.
Fold into dry ingredients until just combined. Don’t over-mix.
Gently stir in walnuts if desired.
Transfer the batter into a non-stick 6- 7” round baking pan and place the pan inside the air fryer basket. (you can also use the square, tall sided pan that came with your air fryer or any similar size air fryer-safe pan.)
Bake at 310 degrees for 33 to 37 minutes, or until toothpick test in the middle of the bread is clean.
Allow to cool in the baking pan on a wire rack for at least 20 minutes before removing.