Preheat the air fryer to 380°F (193°C) for 3 to 5 minutes.
Pat the chicken breasts dry with paper towels. If they are thick, pound them to an even thickness.
In a small bowl, mix the smoked paprika, garlic powder, onion powder, chili powder, cumin, salt, and black pepper.
Brush the chicken breasts with olive oil, then coat both sides evenly with the seasoning mixture.
Place the chicken in the air fryer basket in a single layer.
Air fry for 10 minutes, then flip the chicken.
In a small bowl, stir together the barbecue sauce, brown sugar (if using), and Worcestershire sauce.
Brush the tops of the chicken breasts generously with the BBQ sauce mixture.
Air fry for another 6 minutes, then flip the chicken and brush the other side with more BBQ sauce.
Cook for an additional 2 to 4 minutes, or until the chicken reaches an internal temperature of 165°F (74°C) and the sauce is caramelized.
Let the chicken rest for 5 minutes, garnish with fresh parsley, and serve.