Dice the butter into ¼" by ¼" and refrigerate until ready to use.
In a large bowl: combine flour, salt, sugar, baking powder and COLD butter. Use a pastry cutter or your hand to mix until it begins to form coarse crumbs.
Add milk and knead the dough in the bowl for a few minutes. The dough will be sticky at first but once you knead everything it will be fine. If the dough is still sticky add 1 tbsp of flour and knead until it is no longer sticky.
Preheat the air fryer to 380°F.
Transfer the dough to a floured surface. Pat the dough out to ¾" to 1" thick. Use a biscuit cutter or glass to shape the biscuits. You should have 9-10 biscuits.
Place the biscuits in the air fryer basket and cook for 8 mintues or until golden brown on top. (Depending on the size of your air fryer: repeat this step as necessary).
Optional: brush melted butter or honey over the top of the biscuits.