Slice each trimmed chicken breast in half lengthwise to make four thinner cutlets. Place each cutlet between two sheets of plastic wrap or inside a resealable bag and gently pound with a meat mallet or rolling pin to an even thickness of about 1/4 inch.
In a shallow dish, whisk together the 1/2 teaspoon kosher salt, 1/2 teaspoon garlic powder, and 1 teaspoon dried Italian herb blend. Add the 1/4 cup low-fat Italian dressing and stir to combine.
Place the cutlets in the marinade, turn to coat both sides, then cover and refrigerate for at least 1 hour.
In a separate shallow dish, combine the 3/4 cup whole-wheat breadcrumbs and 2 tablespoons grated Parmesan cheese.
In another shallow dish, beat the 1 large egg until uniform.
Remove the cutlets from the refrigerator. Working one at a time, lift a cutlet from the marinade and let excess marinade drip back into the dish; discard any remaining marinade. Dip the cutlet into the beaten egg, letting excess egg drip off, then press both sides into the breadcrumb–Parmesan mixture so each cutlet is evenly coated. Repeat with remaining cutlets.
Preheat the air fryer to 400°F.
Arrange the breaded cutlets in a single layer in the air-fryer basket without overcrowding (work in batches if needed). Air fry at 400°F for 4 minutes.
Carefully flip each cutlet, lightly spray the top with olive oil spray, and air fry for another 4 minutes, or until the cutlets are golden brown and an instant-read thermometer inserted into the thickest part reads 165°F.
Remove the cutlets from the air fryer, let rest briefly, and serve hot.