Pat chicken dry and pound to even thickness.
Season both sides with salt, black pepper, garlic powder, and Italian seasoning.
Set up breading station with flour in one bowl, whisk eggs and milk in another, and mix panko with Parmesan in a third.
Dredge each chicken piece in flour, shake off excess, dip into egg mixture, then coat thoroughly with breadcrumb mixture, pressing gently to adhere.
Preheat air fryer to 375°F (190°C).
Lightly spray chicken with cooking spray and air fry for 10 to 12 minutes, flipping halfway, until golden and cooked through.
Spoon marinara sauce over each chicken piece, then top with mozzarella and Parmesan cheese.
Return chicken to air fryer and cook 3 to 4 minutes until cheese is melted and bubbly.
Garnish with fresh herbs if desired and serve hot over pasta or alongside a salad.