Prepare a baking sheet by lining it with parchment paper and set it aside. To maintain warmth for the meatballs while cooking multiple batches, preheat the oven to 300°F and line another baking sheet with parchment paper.

In a spacious mixing bowl, combine the Parmesan, breadcrumbs, parsley, salt, Italian seasoning, garlic powder, onion powder, black pepper, and red pepper flakes. Mix thoroughly until all ingredients are well blended.

Add chicken into the mixture. In a separate small bowl, whisk the egg, then add it to the larger bowl (you can also crack it directly into an open area of the big mixing bowl and lightly beat it there). Using a fork or your hands, gently combine the ingredients until evenly mixed, taking care not to compress the meat.

Divide the mixture into portions and form them into meatballs about 1 1/2 inches in diameter (you should end up with around 20 meatballs). Place them on the prepared baking sheet.

Preheat the air fryer to 400°F and spray the basket generously with non-stick cooking spray. Place the meatballs in a single layer in the basket, making sure they don't touch each other to allow proper air circulation (you may need to cook them in multiple batches). Lightly mist the tops of the meatballs with non-stick spray.

Air fry the meatballs at 400°F for 8 to 9 minutes, pausing halfway through to carefully turn them over using tongs. The meatballs are ready when they reach an internal temperature of 165°F as measured with an instant-read thermometer. When cut in half, the meat should appear fully cooked.

Transfer the first batch of cooked meatballs to the second clean baking sheet and place it in the oven to keep them warm. Continue this process with the remaining meatballs.

While the meatballs are air frying, heat the sauce on the stove and prepare any additional items you'd like to serve alongside. Enjoy the meatballs while they're hot, topped with sauce, cheese, herbs, and any other desired accompaniments.