Spray a 12-cup silicone muffin pan with cooking spray. If using metal muffin cups, line them with small squares of parchment paper for easy removal.
Unroll pie crusts and use a 3-inch round cutter to cut 12 circles (you may need to re-roll scraps). Press circles gently into the prepared muffin cups.
In a medium bowl, whisk together eggs, heavy cream, milk, salt, pepper, and garlic powder until well combined.
Divide ham, cheese, green onions, and bell pepper evenly among the pastry cups, filling each about halfway.
Pour egg mixture over the fillings, filling each cup about 3/4 full (they will puff up during cooking).
Preheat air fryer to 300°F. Place muffin pan in the air fryer basket (you may need to work in batches depending on your air fryer size).
Air fry for 12-15 minutes until quiches are set in the center and lightly golden on top. Let cool for 5 minutes before removing from pan. Serve warm or at room temperature.