In a bowl, combine the buttermilk and chicken pieces. Let them marinate for at least 30 minutes, or up to 2 hours in the refrigerator for extra flavor.
In a separate shallow dish, mix together the flour, ranch seasoning, garlic powder, onion powder, paprika, salt, and black pepper.
In another shallow dish, place the panko breadcrumbs.
Remove the chicken from the buttermilk, allowing excess to drip off. Dredge each piece in the flour mixture, then dip it back into the buttermilk, and finally coat it with the panko breadcrumbs. Press the breadcrumbs onto the chicken to ensure they stick well.
Preheat the air fryer to 400°F. Lightly spray the air fryer basket with cooking spray.
Arrange the chicken bites in a single layer in the air fryer basket, making sure not to overcrowd. Lightly spray the tops of the chicken bites with cooking spray.
Cook for 10-12 minutes, flipping halfway through, until the chicken is golden brown and cooked through (internal temperature should reach 165°F).
Serve warm with your favorite dipping sauce.