Allow chicken to cool - It's important that previously cooked fried chicken is at room temperature before being placed into the hot air fryer, otherwise it can steam and result in soggy chicken with soft skin.
Cut larger pieces into smaller nuggets or strips - For best and most even results, cut any larger chicken pieces like breasts or thighs into smaller 1-2 inch chunks or strips before air frying. The smaller the better for getting crispy.
Coat with oil - Use a oil sprayer bottle, brush, paper towel or your fingers to lightly coat the chicken pieces all over with a thin layer of high heat oil. This helps achieve crispy skin when reheating.
Season (optional) - At this point, feel free to sprinkle or drizzle on any extra seasonings or sauces as desired for added flavor.
Arrange in single layer in basket - Place the oiled chicken pieces in the basket of the air fryer. The pieces of fried chicken should be in a single layer without overcrowding. Work in batches for even cooking if needed.
Air fry at 365-375°F - Cook chicken for 6-8 minutes at a temperature between 365-375°F until hot throughout and crispy on the outside, flipping the pieces over halfway through cooking. Depending on the size of your chicken pieces, air fryer chicken for 4-5 minutes per side, up to 5-6 minutes per side for large chicken breast or thigh pieces.
Check internal temperature - For food safety, use an instant read thermometer to check that the internal temperature of the chicken reaches 165°F.
Allow to rest - Once air fried hot and crispy, let chicken pieces rest for 3-4 minutes out of the air fryer before biting in for optimum juicy texture.
Repeat as needed - Cook any remaining chicken in additional batches.