Preheat your air fryer to 400° F for 3-5 minutes.
While your air fryer is preheating, add flour, baking powder, baking soda, salt and sugar to a medium-sized mixing bowl.
Whisk together until combined.
Cut up cold butter into tablespoons and add to the flour mixture.
Using a pastry blender or your fingers, blend the butter into the flour mixture.
Blend until the butter is broken down into course crumbs the size of peas.
With a large spoon, make a well into the middle of the flour mixture.
Pour the buttermilk into the well.
Mix batter together with a large fork until just blended. Do not overmix.
Sprinkle flour onto a Silpat or your counter.
Turn dough onto Silpat or counter. Knead together with your hands about six turns. Be careful not to knead too much.
Pat into a rectangle.
Fold the left side of the dough over to the middle. Then fold the right side of the dough over to the middle like a letter. Turn the dough horizontal. Carefully pat dough down into another rectangle and fold again.
Pat the dough into a final rectangle and use a floured rolling pin to roll dough to 3/4 inches thick. (If you don't have a rolling pin, you can use your hands to pat into the shape and size needed.)
Using a 3-inch biscuit cutter, press into the dough and down, without rotating the cutter.
You should be able to make about 4 biscuits.
Roll or pat dough again into a small rectangle 3/4 inches thick.
Cut 2 more biscuits. (You will have some dough left to possibly make one more small biscuit.)
Place biscuits into your preheated air fryer so they are not touching. I was able to fit four at a time. (If you have trouble with sticking, you can add some parchment paper to the basket or spray some nonstick cooking spray on it.)
Set air fryer to bake biscuits for about 8-10 minutes until they are golden brown. (As some air fryers are different, you may need to start checking the biscuits at 6 minutes and bake longer from there.)
Melt the last two tablespoons of butter in a microwave-safe bowl for about 12-second increments and brush onto biscuits.
Air fry remaining biscuits and brush with butter. Serve and enjoy!