Pat the duck breasts completely dry with paper towels. Using a sharp knife, score the skin in a crosshatch pattern, cutting through the fat but being careful not to slice into the meat. This is essential for rendering the fat and achieving crispy skin.
In a small bowl, combine the kosher salt, black pepper, garlic powder, smoked paprika, ground ginger, and dried thyme. Rub the spice mixture generously over both sides of each duck breast. Let the duck sit at room temperature for 15 minutes.
In a separate small bowl, whisk together the honey, soy sauce, and dijon mustard to create a glaze. Set aside for later.
Preheat the air fryer to 360 degrees F for 3 minutes. Place the duck breasts skin-side down in the air fryer basket, making sure they are not touching.
Air fry at 360 degrees F for 12 minutes skin-side down. This initial low-and-slow approach renders the fat beautifully and starts building that crispy skin.
Flip the duck breasts skin-side up. Increase the temperature to 400 degrees F and air fry for an additional 5 to 7 minutes for medium-rare to medium doneness. The internal temperature should read 130 to 135 degrees F for medium-rare.
Brush the honey-soy glaze over the duck skin during the last 2 minutes of cooking. Remove the duck from the air fryer and let it rest on a cutting board for 5 minutes - this step is critical for juicy meat.
Slice the duck breasts against the grain into thin slices and serve. The skin should be deeply golden and shatteringly crispy, with the meat pink and juicy inside.