Place chicken breasts in a large bowl.
In a measuring cup or a mixing bowl combine warm water and salt; stir, then pour over chicken breasts. Set aside for 20 to 30 minutes. You can also cover the bowl and refrigerate for up to 6 hours.
In the meantime, stir together salt (optional), ground black pepper, garlic powder, paprika, and oregano.
Take each chicken breast out of the brine and rinse under cold water; pat dry with paper towels.
Spray chicken breasts with cooking oil on all sides.
Sprinkle seasoning blend evenly over the chicken breasts and rub in on all sides.
Place 2 to 3 chicken breasts in the Air Fryer basket. Make sure that there's enough space between the breasts to ensure even cooking.
Cook at 375˚F for 10 minutes.
Using tongs, flip chicken over and continue to cook for 5 to 6 more minutes, or until chicken is cooked through.
Please use an instant read thermometer to check for doneness. Chicken is cooked through when internal temperature reaches 165˚F.
Remove chicken breasts from Air Fryer basket and let rest on a cutting board for 8 to 10 minutes before serving.