Remove the wrappers from the mozzarella string cheese sticks. If you prefer smaller snacks, cut each stick in half. Set them aside on a plate.
Prepare three shallow bowls. Put the flour in the first bowl. In the second bowl, whisk the eggs until smooth. In the third bowl, combine the Panko breadcrumbs, Italian seasoning, garlic powder, and salt.
Dredge each cheese stick in the flour, shaking off any excess. Dip it into the egg wash until fully coated, and finally roll it in the breadcrumb mixture, pressing firmly so the crumbs stick. For an extra-thick crust, dip the stick back into the egg and then back into the crumbs a second time.
Place the breaded mozzarella sticks on a parchment-lined baking sheet. Place the sheet in the freezer for at least 1 hour. This is the most important step; it prevents the cheese from melting before the breading gets crispy.
Preheat your air fryer to 390°F (200°C). Lightly spray the air fryer basket with cooking spray. Place the frozen cheese sticks in a single layer, making sure they do not touch. Spray the tops of the sticks with a little more oil. Cook for 6 to 8 minutes, turning halfway through, until golden brown.