1️⃣ Preheat your 7-quart air fryer to 350°F (175°C) for 5 minutes.
2️⃣ Meanwhile, pat the ribs dry and remove the membrane on the underside: slide a knife under one corner, lift the silver skin, and pull it off with a paper towel for grip.
3️⃣ Cut the rack into four roughly equal sections so they fit comfortably in the basket.
4️⃣ Brush all sides of the rib sections with yellow mustard, using just enough for a thin, even coating.
5️⃣ Generously rub the BBQ seasoning over every surface of the ribs.
6️⃣ Pour 2 tablespoons of water into the bottom of the air fryer basket to help prevent smoking. Arrange the rib pieces in the basket, overlapping if necessary but leaving some space for air to circulate.
7️⃣ Cook for 45–60 minutes, flipping every 15 minutes and adding a splash more water if you notice any smoke. The ribs are done when an instant-read thermometer inserted between the bones reads 180–190°F (82–88°C).
8️⃣ While the ribs cook, whisk together the BBQ sauce and 2 tablespoons water in a small bowl.
9️⃣ Transfer the ribs to a baking sheet or platter, brush them all over with the thinned BBQ sauce, then return them to the air fryer in a single layer (you may need to work in batches).
🔟 Air-fry the sauced ribs at 350°F for 3–5 minutes more, until the sauce is bubbly and just beginning to caramelize. Serve immediately.