Whisk together the pickle juice, milk, garlic powder and onion powder in a large bowl. Add in the chicken tenders and let marinate for 20 minutes, no more than 30 minutes. Remove chicken pieces from marinade (do not discard marinade) and pat dry with paper towels.
To the marinade add in the egg and whisk to combine.
In a separate shallow bowl combine the flour and baking powder. In another bowl combine the cornflakes, breadcrumbs and salt.
Meanwhile preheat your air fryer to 390 degrees F. for 5 minutes.
Coat the chicken tenders in the flour, then dip in the egg mixture and then coat in the cornflake mixture. Place the coated chicken in the basket of your air fryer in a single layer, so they are not touching each other. Give a quick spritz with non-stick spray.
Cook for 11 to 12 minutes, flipping halfway through, until the chicken is golden brown and reaches an internal temperature of 165 degrees F. Serve immediately, or place on a wire rack until all batches are cooked. Reheat for just 1 to 2 minutes in air fryer to warm all chicken tenders together.