In a large bowl, whisk together flour, baking powder, sugar, and salt. Add the cold cubed butter and use your fingers or a pastry cutter to work it in until the mixture resembles coarse crumbs with some pea-sized pieces remaining.
Pour in the cold buttermilk and stir with a fork just until the dough comes together. Do not overmix.
Turn the dough out onto a lightly floured surface and gently pat it to about 3/4-inch thickness. Use a round cutter to stamp out biscuits, re-patting scraps as needed to get about 8 biscuits.
Preheat the air fryer to 330°F (165°C). Place the biscuits in the basket with a little space between each one.
Air fry for 10 to 12 minutes until the biscuits are tall, golden on top, and cooked through in the center.
While the biscuits cook, stir together the melted butter and honey. Brush generously over the hot biscuits as soon as they come out, then sprinkle with a pinch of flaky sea salt and serve warm.