Pat the bone-in chicken breasts completely dry with paper towels, paying extra attention to the skin. Dry skin is essential for getting a really crispy result in the air fryer.
Gently loosen the skin on each chicken breast by sliding your fingers between the skin and the meat, creating a pocket without fully detaching it. Spread the softened butter evenly under the skin of each breast. This adds incredible flavor and helps keep the meat juicy during cooking.
In a small bowl, mix together the garlic powder, smoked paprika, onion powder, dried thyme, salt, and black pepper. Drizzle the olive oil over the chicken and rub the seasoning blend evenly over the entire surface of each breast, including on top of the skin and along the sides.
Preheat the air fryer to 370 degrees F. Place the chicken breasts skin side up in the basket, leaving space between them for proper air circulation.
Air fry for 25 to 30 minutes without flipping, until the skin is deeply golden and crispy and the internal temperature at the thickest part of the breast reads 165 degrees F. If the skin is not quite as crispy as you like, increase the temperature to 400 degrees F for the final 2 to 3 minutes.
Remove the chicken from the air fryer and let it rest on a cutting board for 5 minutes before serving. This resting period allows the juices to redistribute, resulting in tender and moist meat with every slice.